Ms. Easty picked up 3 doughnuts and 4 coffees and paid $4.91. Mrs. martin picked up 5 doughnuts and 6 coffees at the same shop and paid $7.59. How much did 1 doughnut cost? How much did 1 coffee cost?
Donuts: $X ea.
Coffee: $Y ea.
Eq1: 3x + 4y = 4.91
Eq2: 5x + 6y = 7.59
Multiply Eq1 by 5 and Eq2 by (-3):
+15x + 20y = +24.55
-15x - 18y = -22.77
Sum: 2y = 1.78, Y = 0.89
In Eq1 replace Y with 0.89:
3x + 4*0.89 = 4.91. X = ?