Question

Elizabeth is holding a dinner party, but she doesn’t have enough plates or cups.

To fix this, she goes to the store and buys p plates and cups.

Given that plates cost $9 and cups cost $7, write an expression for the total cost of all the plates and cups.

Answer 1

Every plate costs $9, so p plates cost $9p (you have to multiply the unit cost of a plate by the number of plates you buy).

By the same logic, if a cup costs $7, c cups cost $7c.

The total expense is the sum of the two expenses, so we have

$9p+7c$