Gaira was asked to evaluate the algebraic expression –3.8x + 6 when x = –7.5.

–3.8(–7.5) + 6(–7.5)

28.5 + (–45)

(–16.5)

What mistake did she make? What is the correct answer?

Sample response:

Gaira made a mistake when substituting the value –7.5 in for x. She multiplied both terms of the expression by –7.5 when she should have only multiplied –3.8 by –7.5. The correct answer is 34.5.