A could be 2 while B could be 3, so -2a+3b turns into -4+9, which equals 5.
From what I know you can't really solve a a single equation with two-variables so it's just a matter of trial and error.
Just try plugging in a small number like 2 for a just to try it and you get 8b^2=72.
Divide everything by 8 to isolate b and you get that b^2=9.
Square root everything and you'll find that b=3. This is just one possible combination, I'm sure there are many more but this is obviously the one that was intended to be found.
Now that we know that a=2 and b=3 just plug them into the equation.
-2(2)+3(3)=?
-4+9=?
5
Sorry about having to use this ^ symbol, the equation maker is not working.
