Hey there! :D
We can just add the numbers together to create an equation we can solve.
2x+y-10=0
x-y-5=0
3x-15=0 <== expression added together
3x=15
Divide both sides by 3.
x=5
Now, plug that in to solve for y.
x-y-5=0
5-y-5=0
Add 5 to both sides.
5-y=5
Subtract 5.
y=0
y=0
I hope this helps!
~kaikers