Answer
-14.9
Work Step by Step
We evaluate the expression by substituting the values of $x=5$ and $y=-9$ into the expression,
$0.8x+2.1y$
=$0.8(5)+2.1(-9)$
=$\frac{8}{10}(5)+\frac{21}{10}(-9)$
=$\frac{40}{10}-\frac{189}{10}$
=$\frac{40-189}{10}$
=$\frac{-149}{10}$
=$-14.9$
