Solve the original equation(5y-7x=35) to get "y" on one side of the equation alone. I did this by first adding 7x to both sides giving you 5y=7x+35. Then, in order to get y by itself on one side of the equation I divided both sides by 5 and got:
y= (7/5)x + 7.
This equation is now in the y=mx+b format. b=the y-intercept. So, according to our equation, the y intercept = 7. Hope this helped!