# CLOTHING A clothing store has all shirts on sale for

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```					Lesson 7-2

Example 1 Use a Table of Ordered Pairs
Find four solutions of y = 3x + 2
x     y = 3x + 2         y       (x, y)
Choose four values for x. Then substitute each value into the               0    y = 3(0) + 2        2       (0, 2)
1    y = 3(1) + 2        5       (1, 5)
equation and solve for y.
2    y = 3(2) + 2        8       (2, 8)
3    y = 3(3) + 2       11      (3, 11)

Four solutions are (0, 2), (1, 5), (2, 8), and (3, 11).

Real-World EXAMPLE
Example 2 Solve an Equation for y
CLOTHING A clothing store has all shirts on sale for \$10 and pants for \$20. Find four
solutions of 10x + 20y = 100 in terms of the numbers of shirts x and pants y McKenzie can
buy with \$100. Explain each solution.

First, rewrite the equation by solving for y.

10x + 20y = 100                     Write the equation.
10x + 20y – 10x = 100 – 10x              Subtract 10x from each side.
20y = 100 – 10x               Simplify.
100 10 x
y=       −                 Divide each side by ten.
20     20
1
y=5– x                     Simplify.
2
1
Choose four x values and substitute them into y = 5 − x .               x       y=5−
1
x      y        (x, y)
2                                 2
(0, 5)         She can buy 0 shirts and 5 pants.                                      1
0       y=5–     (0) 5           (0, 5)
(2, 4)         She can buy 2 shirts and 4 pants.                                      2
(4, 3)         She can buy 4 shirts and 3 pants.                       2       y=5–
1
(2) 4           (2, 4)
2
 1
 9,          This solution does not make sense because she                          1
 2                                                                    4       y=5–     (4) 3           (4, 3)
cannot buy half a pair of pants.                                       2
1              1
9       y=5–     (9) 1        9, 
2              2
Example 3 Graph a Linear Equation
Graph y = -x + 3 by plotting ordered pairs.
x     y = -x + 3     y   (x, y)
First, find ordered pair solutions. Four                   -1   y = -(-1) + 3   4   (-1, 4)
solutions are (-1, 4), (0, 3), (1, 2), and (2, 1).         0    y = -(0) + 3    3   (0, 3)
1    y = -(1) + 3    2   (1, 2)
2    y = -(2) + 3    1   (2, 1)

Plot these ordered pairs and draw a line through them.
Note that the ordered pair for any point on this line is a
solution of y = -x + 3. The line is a complete graph of the
function.

CHECK It appears from the graph that (4, -1) is also a
solution. Check this by substitution.
y = -x + 3           Write the equation.
?
-1  –(4) + 3            Replace x with 4 and y with –1.

-1 = -1                 Simplify.

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