Pre-Algebra Demystified

CHAPTER 11 Graphing 209

Hence, (4, 2) is a solution to 3x
y¼10.

Math Note: The solution can be checked by substituting both

values in the equation:

3x
y¼ 10

3 ð 4 Þ
 2 ¼ 10

12 
 2 ¼ 10

10 ¼ 10

EXAMPLE

Given the equation 5x
2y¼16, find y when x¼4.

SOLUTION
Substitute 4 in the equation and solve for y:

5x
2y¼ 16

5 ð 4 Þ
2y¼ 16

20 
2y¼ 16

20 
 20 
2y¼ 16 
 20


2y¼
 4


2y


 2

¼

4

2

y¼ 2

Hence, when x¼4, y¼2. The ordered pair (4, 2) is a solution for 5x
2y
¼16.

PRACTICE

1. Find y when x¼5 for 3xþ4y¼ 27


2. Find y when x¼
   1 for xþ3y¼ 14


3. Find y when x¼0 for 5xþ2y¼ 20


4. Find y when x¼3 for
   2xþy¼ 10


5. Find y when x¼
   4 for 3x
   2y¼ 10

ANSWERS

1. y¼ 3


2. y¼ 5


3. y¼ 10


4. y¼ 16


5. y¼
   11