To solve this problem, we can set two equations.
Let x be the cost of coffee and y be the cost of latte.
Two coffees and one latte: 2x + y = 10.50
y=10.50 - 2x ...(1)
Three coffees and two lattes: 3x + 2y = 17.00...(2)
Put (1) into (2), we have:
3x + 2(10.50-2x) = 17.00
3x + 2(10.50) - 2(2x) = 17.00
3x + 21 - 4x = 17
Put the unknown to one side:
3x -4x = 17 - 21
-x = -4
When there are negative numbers on both sides, we can take the negative signs away:
x= 4
Therefore, cost of one coffee is A. $4.00.
Hope ot helps!