Can someone with this question?

beth leaves her home on her bike traveling down a long country road at the rate of 8mph. her brother brandon left 15 minutes later after beth on his golf cart along the same country road traveling 12 mph. how long will it take brandon to catch up with beth?
i know the answer is 30 minutes but i have no idea how to get to the answer..
can you explain?

Write two subtraction equations that are equivalent to 5 + 12 = 17.

1- is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis. 2- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis. 3- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in part b?

Which of the following describes the symmetry of the graph of y = x3?