3 apple + 7 blackberrys = 99
2 apple + 14 blackberrys = 178
Then now find
apples = (99 - 7 B)/3 = (178 - 14B)/2
Now make cross multiply
(99 - 7B) •2 = (178 - 14B) •3
Solve parenthesis, use a (b+c) = ab + ac
Then
198 - 14B = 534 - 42B
Now find Blackberrys B PRICE
42B - 14B = 534 - 198
28B = 336
B= 336/28 = 12
Now find Apples price
Apples= ( 99 - 7B) /3 = (99 - 7•12)/3 = 15/3= 5
Then final answer is
Apple's price= $5
Blackberry's price= $12