Question 24727
Use substitution.
Since y=4x, substitute that fact into the 
2nd equation to get the following:
  x+ (4x) = 5 
   5x = 5
    x = 1
Then, since y=4x you get y=4(1)= 4
So, there is one solution: x=1, y=4

Cheers,
stan H.