3. A number decreased by 7 is equal to fifteen.

A. z + 7 = 15
B. z - 7 = 15
C. 7x - z = 15
D. 7z - z = 15

4. In 5n + 6m, which are the variables?

A. 5 and n
B. 6 and m
C. m, n and 2
D. n and m

5. Lance’s age is 8 + z more than her sister, what do you call z?

A. Constant
B. Equation
C. Variable
D. Expression