Answer
$5$
Work Step by Step
Combining like terms, the given expression simplifies to:
$5x-7y-8x+3y$
=$5x-8x+3y-7y$
=$x(5-8)+y(3-7)$
=$-3x-4y$
We then substitute $x=9$ and $y=-8$ in the expression and simplify:
$-3x-4y$
=$-3(9)-4(-8)$
=$-27+32$
=$5$
