You're trying to solve this, right?
First, isolate the variable from the first equation.
4x+y=25
y=-4x+25
Then, substitute in the variable into the second equation.
x-3(-4x+25)=-10
x+12x-75=-10
13x=65
x=5
Now, substitute the x back in to the first equation.
4(5)+y=25
20+y=25
y=5
So, y=5 and x=5.
Hope this helped!