Solve 5x - 9 = 2x + 12.

• A. 7
• B. -7
• C. 3
• D. 9

Answer: (A)

Solving linear equations means using inverse operations to isolate the variable and get all x terms on one side with the constants on the other. Start by moving the constant term from the left to the right: add 9 to both sides to get 5x = 2x + 21. Next, move the x-term on the right to the left: subtract 2x from both sides to obtain 3x = 21. Finally, divide both sides by 3 to solve for x, giving x = 7. You can check by plugging back: 5(7) - 9 = 26 and 2(7) + 12 = 26, so both sides match. The value 7 is the only one that satisfies the equation, since other numbers won’t make both sides equal when substituted.