math
posted by at a lost .
use substitution to solve system
2x+y= 9
=5x+4y= 30

hmmm. you must really be confused; not only at a loss, but at a lost!
we see that
2x+y = 9, so
y = 2x9
now substitute that into the other equation:
5x+4(2x9) = 30
13x = 6
x = 6/13
so, y=2x9 = 105/13
The =5x+4y confuses me. If that was supposed to be 5x, then
5x+4(2x9) = 30
3x = 6
x=2
which seems like a better answer.