Solve (x + 8)/3 = 7 (Step by Step)

How to solve the two-step equation (x + 8)/3 = 7, where x + 8 is divided by 3, with every step explained and a quick check of the answer.

Here 8 is added to x first, and then the whole thing is divided by 3. Undo them in reverse order: undo the divide by 3 by multiplying by 3, then take away the 8.

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Step-by-step solution

Solve (x + 8)/3 = 7

Start with the equation: (x + 8)/3 = 7.
Multiply both sides by 3 to undo the ÷ 3: ((x + 8)/3) × 3 = 7 × 3, so x + 8 = 21.
Subtract 8 from both sides to undo the + 8: x + 8 − 8 = 21 − 8, so x = 13.
Check your answer: put x = 13 back in. (13 + 8)/3 = 21/3 = 7. Both sides match, so x = 13 is correct. ✓

Answer: x = 13

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Frequently asked questions

Why multiply by 3 first?

The brackets mean the whole x + 8 is divided by 3. Dividing happened last, so it is undone first: multiply both sides by 3 to get x + 8 = 21.

Why subtract 8 instead of adding it?

The equation adds 8 to x. Subtracting 8 undoes that, so the + 8 and − 8 cancel and leave x by itself.

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