Answer:
The correct answer is that a rose bush costs $10 and a shrub costs $4
Step-by-step explanation:
To solve this, start by writing equations for what each spent. Use x for the cost of a rose bush and y for the cost of a shrub. Below would be the equations for each.
Rob: 8x + 5y = 100
Amy: 8x + 8y = 112
Now to find the cost, we multiply Rob's equation by -1 and add them together. This will get x to cancel and allow us to solve for y.
-8x - 5y = -100
8x + 8y = 112
------------------
3y = 12
y = 4
So we know the cost of a shrub is $4. Now we can plug that in to either of the original equations and solve for the rose bush cost.
8x + 5y = 100
8x + 5(4) = 100
8x + 20 = 100
8x = 80
x = 10
Which means that a rose bush costs $10.