One way to look at this is to make 2 equations and treat it as a set of equations. We will make the cost of a donut equal to x, and the cost of a coffee equal to y.
Harold's order:
4x + 2y = 4.08
Melinda's order:
2x + 3y = 3.92
To combine these equations, we need to cancel out either x or y:
4x + 2y = 4.08
2x + 3y = 3.92
4x + 2y = 4.08
4x + 6y = 7.84
4x + 2y = 4.08
-4x - 6y = -7.84
We can now combine these equations:
4x + 2y = 4.08
-4x - 6y = -7.84
-4y = -3.76
y = 0.94
Therefore the cost of a large coffee is $0.94. We can plug this into either original equation to find the cost of a donut.
4x + 2y = 4.08
4x + 2(0.94) = 4.08
4x + 1.88 = 4.08
4x = 2.20
x = 0.55
The cost of a donut is $0.55, and the cost of a large coffee is $0.94.
