4 to the 18th power is the answer to your question.
Runner = 5 mph
bicyclist...4 times the runner....4(5) = 20 mph
20 - 5 = 15 mph <== the difference
ANSWER

EXPLANATION
The given quadratic equation is

We compare this to

to get a=4, b=-10, and c=5.
The quadratic formula is given by

We substitute these values into the formula to get:

This implies that




The solutions are:
