Math Word Problems Demystified - A Self Teaching Guide

Substitute in the second equation and solve forx.

2 x
 3 y¼
 4

2 x
 3 ð 7 
 5 xÞ¼
 4

2 x
 21 þ 15 x¼
 4

17 x
 21 ¼
 4

17 x
 21 þ 21 ¼
 4 þ 21

17 x¼ 17

171 x

171

¼

17

17

x¼ 1

Findy:

5 xþy¼ 7

5 ð 1 Þþy¼ 7

5 þy¼ 7

5 
 5 þy¼ 7 
 5

y¼ 2

2. Solve the second equation forx.

xþ 3 y¼ 9

xþ 3 y
 3 y¼ 9 
 3 y

x¼ 9 
 3 y

Substitute in the first equation and solve fory.

 4 xþ 5 y¼
 2

 4 ð 9 
 3 yÞþ 5 y¼
 2

REFRESHER V Systems of Equations 203