How do you solve this equation for y 5x-10y=-40

What is the area of triangle abc if a = 8, b = 11, and c = 15?

Abby is preparing fruit punch for her party. she starts with a bowl filled with liquid that has 1/2 fruit juice and 1/2 sprite, but she decides it's too fruity. so she pours out 1/4 of the liquid, and then fills the bowl up again with sprite. what fraction of the punch is now sprite?

Just tell me how to set up the equation.