The correct option is (c) $(33q + 1).
Let's represent the cost of the first book as $(7m + 2) and the cost of the second book as $18.
To find the total cost, you add these two amounts:
Total cost = $(7m + 2) + $18
To simplify, combine like terms:
Total cost = $7m + 2 + $18
Combine the constants:
Total cost = $7m + 20
Now, the given options are in the form $(qm + n), so let's write the total cost in that form:
Total cost = $7m + 20
= $(7m + 0) + 20
= $(7m + 1 * 20)
Now, compare this with the given options:
a. $(21q + 1)
b. $(31q + 1)
c. $(33q + 1)
d. $(39q + 1)
The correct option is (c) $(33q + 1).