F(x) = x^2 +2*7x + 40
.. = (x^2 +2*7x +7^2) +(40 -7^2)
.. = (x +7)^2 -9
f(x) = (x +7)² -9
The number of failures in 3000 hours with an MTBF of 6 hours is 500. When the MTBF is 8 hours, the number of failures drops to 375, a savings of the cost of 125 failures, or $25,000.
First combine like terms. Add -24 and 8.
You end up with -16+w=4
Now, move 16 by doing the opposite to both sides.
w=20