Question

Liliana solved the equation below. When she tried to verify her answer, she realized she made an error.

One-third (x + 18) = 7
One-third x + 6 = 7
One-third x + 6 minus 6 = 7 + 6
One-third x = 1
x = 3

Which correction should Liliana make?
The first step should be One-third x + 54 = 7.
The second step should be One-third x + 6 minus 6 = 7 minus 6.
The third step should be One-third x = 13.
The final step should be x = one-third.

Answer 1

Choose the second correction.

Work: (1/3)(x + 18) = 7 → (1/3)x + 6 = 7. Subtract 6 from both sides: (1/3)x + 6 − 6 = 7 − 6, so (1/3)x = 1. Multiply by 3: x = 3.

Liliana mistakenly added 6 to the right side instead of subtracting it.