L5 · Solving One-Operation Equations

Learning goal

“I can solve an equation with one operation by doing the same thing to both sides, and I can check my answer by putting it back into the equation.”

Solve — find the value of the unknown that makes an equation true.

Inverse operation — an operation that undoes another: subtraction undoes addition, addition undoes subtraction, division undoes multiplication, multiplication undoes division.

Check — putting your answer back into the original equation to prove both sides are equal.

Worked example

Solve n + 8 = 20. Step 1: The 8 is ADDED to n. The inverse operation is subtraction. Step 2: Subtract 8 from BOTH sides (L4's rule): n = 20 - 8 = 12. Step 3: Check: 12 + 8 = 20. Solved and proven. Second example: m - 9 = 14. The 9 is SUBTRACTED, so add 9 to both sides: m = 14 + 9 = 23. Check: 23 - 9 = 14. Say it plainly: to free the unknown, undo the operation that is attached to it - with the inverse operation, on both sides, every time.

Check yourself — explain it

In m - 9 = 14, we add 9 to both sides because...

Paired problem — example still visible

Solve n + 7 = 19 -> n = 12 (subtract 7 from both sides; check: 12 + 7 = 19)

Faded completion — last step is yours

"k - 6 = 15. Add 6 to both sides; then k = ___" -> 21

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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