Please answer me .....

Answer:
a. 2x -3
b. 7
Step-by-step explanation:
a. The expression that represents the difference is sales between the two sales will be:
9x - (7x + 3) = 9x - 7x - 3 = 2x - 3
b. What we do here is to simply substitute the value of 5 for x
mathematically, we have to substitute the value of 5 in the expression above
We have this as:
2(5) -3
= 10-3 = 7