Solve for x: 2x + 5 = 17.

Solve for x: 2x + 5 = 17.

• A. x = 6
• B. x = 12
• C. x = -6
• D. x = 1

Answer: (A)

Isolating the variable in a linear equation is what you’re practicing here. To get x by itself, undo what’s been done to it. Subtract 5 from both sides to remove the plus 5: 2x = 12. Then undo multiplying by 2 by dividing both sides by 2: x = 6. A quick check shows 2(6) + 5 = 12 + 5 = 17, which matches the right side. If you try other values, they don’t satisfy the equation (for example, x = 12 gives 29, x = -6 gives -7, x = 1 gives 7), so the only solution is x = 6.

Isolating the variable in a linear equation is what you’re practicing here. To get x by itself, undo what’s been done to it. Subtract 5 from both sides to remove the plus 5: 2x = 12. Then undo multiplying by 2 by dividing both sides by 2: x = 6. A quick check shows 2(6) + 5 = 12 + 5 = 17, which matches the right side. If you try other values, they don’t satisfy the equation (for example, x = 12 gives 29, x = -6 gives -7, x = 1 gives 7), so the only solution is x = 6.