If y = 2x + 3, what is y when x = 4?

• A. y = 8
• B. y = 10
• C. y = 12
• D. y = 11

Answer: (D)

Evaluating a linear expression by substitution. For y = 2x + 3, plug in x = 4: 2 times 4 is 8, then add the constant 3 to get 11. So y equals 11. The other numbers come from small missteps: 8 would happen if the +3 were ignored, 10 if you added 2 instead of 3, and 12 if you added 4 instead of 3. But with the given expression, 11 is the correct result.