# Dollar bills and system of two linear equations

by Kendall Whiteside
(Happy Valley, Oregon)

“A student has some \$1 bills and \$5 bills in his wallet. He has a total of 15 bills that are worth \$47. How many of each type of bill does he have? ”

Let x be the number of \$1 bills and y be the number of \$5 bills.

The number of \$1 bills plus the number of \$5 bills equal 15 or x + y = 15

Worth of \$1 bills plus worth of \$5 bills = \$47 or 1x + 5y = 47

Therefore, just solve the system of equations below.

x + y = 15 (1)

x + 5y = 47 (2)

(2) minus (1) will give 4y = 32

y = 8 since 4 × 8 = 32

x + 8 = 15

x = 7

The student has seven \$1 bills and eight \$5 bills.

## Recent Articles

1. ### Fundamental Counting Principle

Jun 06, 23 07:32 AM

The fundamental counting principle is introduced in this lesson. Learn how to count with the multiplication principle and the addition principle.

2. ### 45-45-90 Triangle

May 01, 23 07:00 AM

What is a 45-45-90 triangle? Definition, proof, area, and easy to follow real-world examples.