Answer:
.009 miles/hour
Step-by-step explanation:

This is the method you should take with unit conversions in general, just set up fractions so the units cancel out, like the 7.5 feet cancels out with the feet in the 1/5280 so miles is left on top.
X^2+8x+x+8 simplifies to x^2+9x+8
The square root of 64 is 8 but put 8 to the 1/2 power
The answer is 4
The speed of the 747 jet is 545MPH and the speed of the 787 jet is 530MPH. that means the 747 jet is faster by 15MPH