Explanation:
Let,
Cost of blueberry pie = x
Cost of lemon meringue = y
13x + 12y = 285 (1)
3x + 12y = 195 (2)
=> 13x + 12y - (3x + 12y) = 285 - 195
=> 13x + 12y - 3x - 12y = 90
=> 10x = 90
=> x = 90/10
=> x = $ 9
From 2
3(9) + 12y = 195
=> 27 + 12y = 195
=> 12y = 195 - 27
=> 12y = 168
=> y = 168/12
=> y = $ 14