7,5x+y-8,5x-3,5y

To simplify the expression 7.5x + y - 8.5x - 3.5y, combine like terms:

First, combine the x terms: 7.5x - 8.5x = -1x or -x

Then, combine the y terms: y - 3.5y = -2.5y

So the simplified expression is -x - 2.5y.