15 times the difference of brants speed and the wind speed

Anyone know? will mark brainliest if correct!

1- 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.2- 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 the first question?

Acyclist bike x distance at 10 miles per hour .and returns over the same path at 8 miles per hour. what is the cyclist average rate for the round trip in miles per hour ?