I don't get how to solve this part.. the result should be 48.. would anyone explain, thanks
Sorry but I can't really see the problem.
You've just worked it out yourself to get y=-11, isn't that the question done?
Anyway, if you have it must be equal to something in order for it to have solutions.
Are you trying to solve:
You can solve this by:
A good start for solving this proportion is to "cross-multiply" to get:
. . . . .3(5 - y) = 6(8)
Solve the resulting linear equation by first multiplying things out:
. . . . .15 - 3y = 48
Rearrange to get:
. . . . .15 - 48 = 3y
. . . . .-33 = 3y
Then divide through. To confirm your solution, plug it back in to the original equation:
. . . . .left-hand side: 3/8
. . . . .right-hand side: 6/(5 - [-11]) = 6/(5 + 11) = 6/16 = 3/8
And you're done!