Math Word Problems Demystified - A Self Teaching Guide

Substitute the value ofxin the second equation and solve forysince

x¼yþ8.

xþ 3 ¼ 2 ðyþ 3 Þ

ðyþ 8 Þþ 3 ¼ 2 ðyþ 3 Þ

yþ 8 þ 3 ¼ 2 yþ 6

yþ 11 ¼ 2 yþ 6

y
yþ 11 ¼ 2 y
yþ 6

11 ¼yþ 6

11 
 6 ¼yþ 6 
 6

5 ¼y

Select the first equation, lety¼5, and solve forx.

x¼yþ 8

x¼ 5 þ 8

x¼ 13

Hence, Bill is 13 years old and his brother is 5 years old.

EVALUATION: Check the second equation forx¼13 andy¼ 5

xþ 3 ¼ 2 ðyþ 3 Þ

13 þ 3 ¼ 2 ð 5 þ 3 Þ

16 ¼ 2 ð 8 Þ

16 ¼ 16

EXAMPLE:A person walked from his home to the football stadium at a rate

of 3 miles per hour. After the game, he rode the bus back the same way at a

rate of 22 miles per hour. If the total trip took 2 hours, how far did he walk?

214 LESSON 18 Using Two Equations