Answer:
y=-x
Step-by-step explanation:
It's going left one by one, meaning the slope is negative and has a slope of -1 or -x.
I see your last line is : c(x) = 0.9(x^2-10)^2 + 101.1
Let y = x^2, then c(y) = 0.9(y-10)^2 + 101.1
Apparently, c(y) is a parabola, min is 101.1 when y = 10, max is infinity
So let x^2 = 10 -> x = sqrt(10) or -sqrt(10), min is 101.1, max is infinity
To find this answer, we need to multiply 3.57 by 12.

Therefore, 12 planks will cost $42.84.
Answer:
(24,13)
Step-by-step explanation:
24 is Sarah's age.
13 is Mike's age.
System:

I hope this helped!