Solve 3(x + 2) = 21.
- Distribute: 3x + 6 = 21.
- Subtract 6: 3x = 15; divide by 3: x = 5.
- Check: 3(5 + 2) = 21.
Answer: x = 5
Solve linear equations and check the solution by substitution.
Learn the skill
To solve an equation, find every value that makes both sides equal. Simplify each side, gather variable terms, and use inverse operations on both sides. Substitution into the original equation checks the result.
Answer: x = 5
Answer: x = 5
Answer: No solution
A student turns −2(x − 3) = 10 into −2x − 6 = 10. What should change?
Multiplying −2 by −3 gives positive 6, so the correct expansion is −2x + 6 = 10.
Subtract 6: −2x = 4. Divide by −2: x = −2.
Check in the original equation: −2(−2 − 3) = −2(−5) = 10. Substitution catches the sign error.
Solve 4 − 3(2x − 1) = 19.
Expand to 4 − 6x + 3 = 19. Combine constants: 7 − 6x = 19, so −6x = 12 and x = −2. The original left side becomes 4 − 3(−5) = 19.
x = −2
Solve these before opening the answers. The printable sets below give you more practice.
1. Solve 4x + 7 = 23.
x = 4
Subtract 7 to obtain 4x = 16, then divide by 4.
2. Solve 3x + 2 = x + 12.
x = 5
Subtract x and 2 to get 2x = 10.
Use inverse operations, signed numbers and the distributive property.
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