Question

-4.5x-2y=-12.15
3.25x-y=-0.75

Answer 1

you could multiply the bottom equation by -2
(that means multiply both sides and *all* terms by -2)
if you do that the bottom equation becomes
\[ -6.5x+2y= +1.5 \]

Answer 2

now add both equations together
(that means add the right sides together, and add the left sides together)

notice that -2y + 2y (on the left side) will add up to zero.