The value of x is given as x = 10 in the system of equations 3x + 5y = 20.
This means that we can substitute x = 10 into the equation 3x + 5y = 20 to solve for y:
3(10) + 5y = 20
30 + 5y = 20
5y = -10
y = -2
Therefore, the solution to the system of equations 3x + 5y = 20 and x = 10 is (x,y) = (10,-2).