To solve this system of equations, we can use the substitution method.

First, we substitute the expression y=5x into the second equation:

5x + y = 20
5x + 5x = 20
10x = 20
x = 2

Now that we have found the value of x, we can substitute it back into the first equation to find the value of y:

y = 5(2)
y = 10

Therefore, the solution to the system of equations is x=2 and y=10.