Need to know how to do this problem

Question

Two cyclists start from the same point and ride in opposite directions. One cyclist rides twice as fast as the other. In 3 hours, they are 81 miles apart. Find the rate of each cyclist.

use substitution or elimination method.

include let statement, equations and solution.

Answer 1

3x + 3y =81

x+y = 27

x=2y

3y =27

y = 9 mph

x = 18 mph