Math Word Problems Demystified - A Self Teaching Guide

IMPLEMENTATION: Solve the system

xþy¼ 8

25 xþ 10 y¼ 125

Find the value ofy in the first equation. Substitute it in the second

equation and solve forx.

xþy¼ 8

x
xþy¼ 8 
x

y¼ 8 
x

25 xþ 10 y¼ 125

25 xþ 10 ð 8 
xÞ¼ 125

25 xþ 80 
 10 x¼ 125

15 xþ 80 ¼ 125

15 xþ 80 
 80 ¼ 125 
 80

15 x¼ 45

151 x

15

¼

45

15

x¼ 3

Findy:

xþy¼ 8

3 þy¼ 8

3 
 3 þy¼ 8 
 3

y¼ 5

Hence, there are 3 quarters and 5 dimes.

212 LESSON 18 Using Two Equations