No idea how to do this equation. its applying system's of linear equations.
1.5x-1.9y=-29
x-0.9y=4.5

What you want to do is take one of the 2 equations and isolate one variable. you will then use the value that you find for the variable and plug it back into the other equation. here is how:

This would be easiest to do with the second equation in the set since the x is not being multiplied by anything. So lets isolate the x in the second equation.

add 0.9y to both sides and you get:

x=4.5+0.9y

we now know what x is equal to in terms of y. so lets replace the x in the first equation with the new value. You get:

1.5(4.5+0.9y)-1.9y=-29

Now just solve for y:
6.75+1.35y-1.9y=-29
1.35y-1.9y=-35.75
-0.55y=-35.75
y=65

so now you know that y=65 so plug 65 in as y in the second equation to find x

x-0.9*65=4.5

Now simply solve for x

x-(-58.5)=4.5
x+58.5=4.5
x=-54

Hope this helped! :)