4 pencils and 3 crayons are 20.7 inches. 5 pencils and 4 crayons are 26.4 inches. Each pencil is the same length as the other pencils, and each crayon is the same length as the other crayons. What is the length of 1 pencil? What is the length of 1 crayon?

5x + 4y = 26.4 inches -> 15x + 12y = 79.2 inches.

We minus the top one from the bottom -> x = 82.8 – 79.2 = 3.6 inches

Replace back : 4 x 3.6 + 3y = 20.7

14.4 + 3y = 20.7

3y = 6.3

y = 2.1

So, the length of 1 pencil is 3.6 inches, the length of 1 crayon is 2.1 inches

Recheck : 4 pencils and 3 crayons = 3.6 x 4 + 2.1 x 3 = 14.4 + 6.3 = 20.7

5 pencils and 4 crayons = 3.6 x 5 + 2.1 x 4 = 18 + 8.4 = 26.4