Math Word Problems Demystified - A Self Teaching Guide

Since reversing the digits gives a new number which is 9 more than the

original number, the equation is

ð 10 xþyÞþ 9 ¼ð 10 yþxÞ

IMPLEMENTATION: Solve the system

xþy¼ 15

10 xþyþ 9 ¼ 10 yþx

Solve the first equation fory, substitute in the second equation and

findx.

xþy¼ 15

x
xþy¼ 15 
x

y¼ 15 
x

10 xþyþ 9 ¼ 10 yþx

10 xþð 15 
xÞþ 9 ¼ 10 ð 15 
xÞþx

10 xþ 15 
xþ 9 ¼ 150 
 10 xþx

9 xþ 24 ¼ 150 
 9 x

9 xþ 9 xþ 24 ¼ 150 
 9 xþ 9 x

18 xþ 24 
 24 ¼ 150 
 24

18 x¼ 126

181 x

181

¼

126

18

x¼ 7

Findy:

xþy¼ 15

7 þy¼ 15

210 LESSON 18 Using Two Equations