5x -4y=-9-3x+4y=15

Question

Algebra problems

Answer 1

5x -4y=-9

-3x+4y=15

Add the equations

2x=6 and so x=3.  Substitute in first equation

15-4y=-9 or -4y=-24 or y=6

 

Answer 2

You provided us with two equations essentially built into one string

equation one is 5x-4y=15 

equation two is -9-3x+4y=15 rewrite as -3x+4y=24

 

So two equations and two unknowns(x, and y) meaning it's doable

Upon solving one equation for one variable either x or y we can then substitute that in the other equation

Giving us the solution x=19.5 and y=20.625