Answer: Choice B
rose bush: $10, shrub: $4
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Work Shown:
x = cost for one rose bush
y = cost for one shrub
Rob's equation: 8x+5y = 100
Amy's equation: 8x+8y = 112
Subtract the equations straight down (match terms)
8x - 8x = 0x = 0, x terms go away
5y-8y = -3y
100-112 = -12
After those three subtractions, we end up with this new equation: -3y = -12
That equation solves to y = 4 when you divide both sides by -3
Use this value of y to find x
8x+5y = 100
8x+5(4) = 100 ... replace y with 4
8x+20 = 100
8x+20-20 = 100-20 .... subtract 20 from both sides
8x = 80
8x/8 = 80/8 ... divide both sides by 8
x = 10
We end up with x = 10 and y = 4 pairing up. The two equations, when graphed, cross at the location (10,4). One rose bush costs $10 and one shrub costs $4.
