PSAT Math Grid-Ins Question 108: Answer and Explanation
Question: 108
q(x) = –
x + 12
Given the function above, what value of c will make q(c) equal to 6?
Correct Answer: 18
Explanation:
18
The question asks for a specific value when the function is equal to 6. In function notation, the number inside the parentheses is the x-value that goes into the function, and the value that comes out of the function is the y-value. Plug x = c into the q function to get 
. The value of q(c) is 6, so this becomes 
. Subtract 12 from both sides of the explanation to get 
, then multiply both sides by –3 to get c = 18. The correct answer is 18.
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