2.5 + 3 = 5.5 total speed
7miles / 5.5 mph = 1.27 hours

Integrating gives

To compute the integral, substitute
, so that
. Then

Since
for all
, we can drop the absolute value, so we end up with

Given that
, we have

so that

Step-by-step explanation:
y = 8x² + 8x - 96
y = 8(x² + x - 12)
y = 8(x + 4)(x - 3)
When y = 0, 8(x + 4)(x - 3) = 0.
=> x = -4 or x = 3. (B)
He currently does 8, and is increasing by 2, so our equation will be
2x+8=30
Subtract the 8 over
2x=22
Divide by 2 on both sides
X=11
It will take 11 days