Solve 4x + 7 = 31 (Step by Step)

How to solve the two-step equation 4x + 7 = 31, where x is multiplied by 4, with every step explained and a quick check of the answer.

Here x is multiplied by 4 and then has 7 added. Undo them in reverse order: take away the 7 first, then divide by 4.

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Step-by-step solution

Solve 4x + 7 = 31

Start with the equation: 4x + 7 = 31.
Subtract 7 from both sides to undo the + 7: 4x + 7 − 7 = 31 − 7, so 4x = 24.
Divide both sides by 4 to undo the × 4: 4x ÷ 4 = 24 ÷ 4, so x = 6.
Check your answer: put x = 6 back in. 4 × 6 + 7 = 24 + 7 = 31. Both sides match, so x = 6 is correct. ✓

Answer: x = 6

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Frequently asked questions

Why subtract 7 before dividing by 4?

The 7 was added last, so it is undone first. If you divide by 4 first, you must divide every term: x + 7/4 = 31/4, which still gives x = 6 but with messier fractions.

How can I check my answer?

Put x = 6 back into the original equation: 4 × 6 + 7 = 31. Both sides are equal, so the answer is right.

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