1. 5.2 Substitution Try this one: x = 4y y = 5x 4x – y = 75 2x + 3y = 34
(2, 10)
x = 4y
4x – y = 75
4(4y) – y = 75
16y – y = 75
15y = 75
y = 5
x = 4(5)
x = 20
Ordered Pair (20, 5)

2. Substitution Method for solving 2 equation with 2 variables
1. x + y = 15
2. x – y = 9
Get one variable by itself so that you can use it to substitute.
Solve the second equation for x = 9 + y
Plug 9 + y into the first equation for x.
(9 + y) + y = 15
9 + 2y = 15
2y = 6
y = 3
x = 9 + 3
x = 12 (12, 3)

3. 2x + 2y = 8
x + y = -2
x = -2 – y
2(-2 – y) + 2y = 8
-4 – 2y + 2y = 8
-4 = 8
FALSE!!
Answer: No Solution
x – 2y = 3
4x – 8y = 12
x = 3 + 2y
4(3 + 2y) – 8y = 12
12 + 8y – 8y = 12
12 = 12
TRUE
Answer: Infinitely Many Solutions

4. Toshiro weighs 12 pounds less than Steve
Toshiro weighs 12 pounds less than Steve. The sum of their weights is 118 pounds. How much does Steve weigh? How much does Toshiro weigh?
Toshiro = T
Steve = S
T = S – 12
T + S = 118
S – 12 + S = 118
2S – 12 = 118
2S = 130
S = 65 pounds
T = 65 – 12
T = 53 pounds

5. Your Turn y = 6x 2x + 3y = -20 x – 2y = 3 3x – 6y = 9 3x + y = 12
Answer: (-1, -6)
x – 2y = 3
3x – 6y = 9
x + 14y = 84
2x – 7y = -7
y = 2x + 6
2x – y = 2
Answer: Infinitely Many
Answer: (7, -9)
Answer: (14, 5)
Answer: No Solution

6. Try These
page 263 #1, 3, 5
1. (5, -1)
3. No Solution
5. (-2, 3)