What is the value of 8 to the third power + 5x when x = 12

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

Which of the following is an example of a rational number? a. π b. √ 9 c. √ 8 d. 3.8362319