Bananas cost: $0.25
Apples cost: $0.30
4b+5a=2.50
10b+3a=3.40
You multiply the equations by the variables so they can cancel out. For example the first one by 3 and the second by 5 so you have
12b+15a=7.50
50b+15a=17
Subtract them and end up with
-38b=-9.5
solve: b=0.25, substitute b in any equation and get a=0.30
Hope this helped