Question

comic books cost $2 each and magazines cost $4 each. if you want to spend exactly $30 and you buy 3 magazines, how many comic books can you buy?
multiply 4·3 on the left side of the equation.
2c + 4m = 30
2c + 4·3 = 30
2c + \square = 30

Explanation:

Step1: Calculate cost of 3 magazines

$4 \times 3 = 12$

Step2: Substitute cost into equation

$2c + 12 = 30$

Step3: Isolate the comic book term

$2c = 30 - 12$
$2c = 18$

Step4: Solve for number of comics

$c = \frac{18}{2}$

Answer:

The missing value in the box is 12, and the number of comic books you can buy is 9.