Question 7670
There is no "solve" of an expression. But you can simplify it; that is, do as much of the arithmetic as possible.
-2(f+3g)+5(6f-2g) 
(-2f -3g)+(30f-10g) [using the distributive law a(b+c)=ab+ac]
30f-2f -3g-10g [rearranging because addition is commutative]
28f-13g [doing the arithmetic]
Can't go any further, because you can't add f's to g's until you know what value each of them stands for.
Done!