Question

you bought 4 bananas and 5 apples at the store for $2.50 the next day you bought 10 bananas and 3 apples at the store for $3.40. The bananas and apples had the same price both days. How much does each cost?

Answer 1

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