Stephanie M. answered 04/23/15
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We can write a system of equations to model this problem. Let x = dollars of merchandise you purchase and let y = how much you actually pay per year. Then:
Plan A: y = 0.7x + 300
Plan B: y = 0.9x + 40
Plan A: y = 0.7x + 300
Plan B: y = 0.9x + 40
Substitute y = 0.7x + 300 into the second equation and solve for x:
0.7x + 300 = 0.9x + 40
300 = 0.2x + 40
260 = 0.2x
1300 = x
So, you would have to purchase x = $1,300 worth of merchandise to pay the same amount.
To find y, plug x = 1300 into the first equation and solve:
y = 0.7(1300) + 300
y = 910 + 300
y = 1210
So, each plan would cost y = $1,210.
Check your answer by plugging those values for x and y into the second equation:
1210 = 0.9(1300) + 40
1210 = 1170 + 40
1210 = 1210
Duane D.
04/23/15