Tyler is using the distributive property on the expression 9 - 4(5x – 6). Here is his

work:

9 - 4(5x - 6)

9+(-4)(5x +-6)

9 +-20x +-6

3 – 20x

Mai thinks Tyler's answer is incorrect. She says, "If expressions are equivalent then

they are equal for any value of the variable. Why don't you try to substitute the same

value for x in all the equations and see where they are not equal?"

a. Find the step where Tyler made an error.

b. Explain what he did wrong.

c. Correct Tyler's work.