Subtract the equations straight down. So we'll subtract the x terms together
5x - 5x = 0x = 0
meaning the x terms effectively go away after subtraction
Then we do the y terms together in the same exact order
y-3y = -2y
Then finally the right hand side values
6 - (-5) = 6+5 = 11
All of that work done indicates we have 0x-2y = 11 which is the same as -2y = 11. Divide both sides by -2 and we end up with y = -11/2
This answer isn't listed so I'm thinking there's a typo your teacher made somewhere.