Page 155 - Math Course 1 (Book 1)

Equations with Variables

Let d represent the number of days. Solve 4x + 15 = 2x – 7.
1
$80 plus $20 for each day equals $120 plus $15 A. 1
for each day 3
B.–3 2
80 + 20d = 120 + 15d Write the 3
original C. –11
equation.
D. –22
80 + 20d – 15d = 120 + 15d – 15d Subtract 15d
from each side. Answer

80 + 5d = 120 Simplify.

80 – 80 + 5d = 120 – 80 Subtract 80
from each side.

5d = 40 Simplify. Solve 2.4 – 3m = 6.4m – 8.88.

5d = 40 Divide each A. 3.3
5 5 side by 5. B. 1.2
C. –0.7
d = 8 Simplify. D. –1.9
Answer
If you rent the car for 8 days, the
Answer
cost is the same for both plans.

Your Turn!

Equations with Variables on Each Side REAL WORLD EXAMPLE

Solve 7x = 5x + 6. Check your solution.
CELL PHONES
A.–3 A cell phone provider offers two plans.
Under plan A, the monthly cost is $20 with
B. 1 a cost of $0.35 per minute. Under plan B,
2 the monthly cost is $35 with a cost of $0.15 per
C. 3 minute. What number of minutes results in the
same cost?
D. 21
A. 30 minutes
B. 75 minutes
Answer C. 110 minutes
D. 275 minutes

Answer

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