The most useful sentence you can give a teacher is “I am sure up to this line, and this is the line I doubt.” It turns “I am lost” into a place, and a place can be fixed.
This page shows a three-part way to say it, using one worked example. It follows on from preparing one specific question before an online class.
Why is “I got lost” so hard to act on?
A teacher who hears “I got lost” has to guess. They might re-teach the whole topic, which wastes your time, or move on, which leaves the problem in place.
A precise description saves both of you. It also helps you, because the act of finding the line often shows you the slip before anyone else says a word.
The three-part description
Write three short statements about one question:
- Last line I trust. The final step where you could explain why it was right.
- First line I doubt. The earliest step where something felt wrong, or the answer looked strange.
- What I expected. What you thought the next step, or the answer, should look like.
You do not need to know what is wrong. You only need to mark the edges of the problem.
Worked example
Question: The length of a rectangle is 3 cm more than its width. The perimeter is 34 cm. Find the area.
Here is one student’s working:
width = x, length = x + 3
x + x + 3 = 34
2x + 3 = 34
2x = 31
x = 15.5The student stopped here, because a width of 15.5 cm and a length of 18.5 cm felt too big.
Last line I trust: “width = x, length = x + 3”. I can explain this.
First line I doubt: “x + x + 3 = 34”. I copied the perimeter but I am not sure that is the perimeter.
What I expected: whole-number sides that look like a normal rectangle.
That description is short, honest and precise. A teacher can see at once that the slip is on line 2: the perimeter adds all four sides, so the equation should be 2(x + x + 3) = 34.
Correct working: 4x + 6 = 34, so 4x = 28 and x = 7. The length is 10 cm and the area is 7 × 10 = 70 cm². Check: perimeter = 2(7 + 10) = 34 ✓.
The mistake to watch for
The common version is a vague report: “I did the equation and it did not work.”
This hides the one piece of information that matters. The student may have mis-set the equation, mis-solved it, or mis-read the question. Those are three different problems with three different fixes.
The correction is to replace every “it did not work” with the three labels. If you truly cannot find a line you doubt, say so, and say what made you stop. “The answer looked too big” is a real observation, and it is where this student started.
Check yourself
1. A student writes: 3x + 5 = 2x − 4, then 3x − 2x = −4 + 5, so x = 1. Write the “first line I doubt” and say why.
Show answer
The doubtful line is the second one. Moving +5 across the equals sign should give −4 − 5, not −4 + 5. The correct result is x = −9. Check: 3(−9) + 5 = −22 and 2(−9) − 4 = −22 ✓.
2. Which is the more useful thing to tell a teacher: “I don’t get simultaneous equations” or “I can eliminate y, but I do not know what to do with the x value once I have it”?
Show answer
The second. It names the last step you can do and the exact step that stops you. The first sends the teacher back to the start of the topic.
3. In the rectangle example, why is checking the perimeter a good way to decide whether to trust x = 15.5?
Show answer
With x = 15.5 the sides are 15.5 and 18.5, so the perimeter is 2 × 34 = 68 cm, not 34 cm. The answer fails its own question, so the working must contain a slip.
Where this leads next
Once you can describe a stuck point, you can arrange a whole lesson around it. The one-hour trial agenda builder helps you place two sticking points inside a time-boxed plan, and reflecting on whether a lesson left room for questions covers the other side of the conversation.
Self-study may be enough when you can find and fix your own slips by checking answers. If you can locate the line but keep not knowing why it fails, how the paid trial works is explained on its own page, and our teachers offer online one-to-one tuition across the Cambridge IGCSE subjects.