posted by at a lost on .
use substitution to solve system
hmmm. you must really be confused; not only at a loss, but at a lost!
we see that
-2x+y = -9, so
y = 2x-9
now substitute that into the other equation:
5x+4(2x-9) = -30
13x = 6
x = 6/13
so, y=2x-9 = -105/13
The =5x+4y confuses me. If that was supposed to be -5x, then
-5x+4(2x-9) = -30
3x = 6
which seems like a better answer.