Okay, so let's break it down step-by-step:
1) distribute the 2 inside the parenthesis (2*x and 2*5) it gives you 2x-10
2)So now you're equation is Y-3=2x-10. You want Y by itself if you want it in Y-intercept form. So add three on each side. 3 cancels out on the right.
Y-3=2x-10
+3 +3
-----------------
Y= 2x+13
3) And there you go, Y=2x+3 is the answer
