x+5y=−15
y=1/5x+1
An easy way to do this is by substitution. The second equation is already set to y, so just plug that into the first equation.
x + 5(1/5x + 1) = -15
x + x + 5 = -15
2x + 5 = -15
2x = -20
x = -10
Now that you've got the x, plug that into one of the equations to find y.
(-10) + 5y = -15
5y = -5
y = -1
So the ordered pair is (-10, -1).