We can re-arrange it into slope-intercept form([tex]\sf~y=mx+b[/tex]).
[tex]\sf~y=10-5x[/tex]
Switch -5x and 10 around:
[tex]\sf~y=-5x+10[/tex]
Now it's in slope intercept form.
[tex]\sf~y=mx+b[/tex]
Where [tex]\sf~m[/tex] is the slope, and [tex]\sf~b[/tex] is the y-intercept.
So in this case, 10 is the y-intercept.
[tex]\sf~y=-5x+\boxed{\sf10}[/tex]