Question 145088
1m + 2d + 1c = 1.85
3d + 2c = 2.30
1m + 1d + 2c = 1.75

1m + 2d + 1c = 1.85
-(1m + 1d + 2c = 1.75)

1m + 2d + 1c = 1.85
-1m - 1d - 2c = -1.75
d - c = .10
d = c + .10

3d + 2c = 2.30
3(c + .10) + 2c = 2.30
3c + .30 + 2c = 2.30
5c + .30 = 2.30
5c = 2.30 - .30
5c = 2.00
c = .40

3d + 2c = 2.30
3d + 2(.40) = 2.30
3d + .80 = 2.30
3d = 2.30 - .80
3d = 1.50
d = .50

1m + 1d + 2c = 1.75
1m + 1(.50) + 2(.40) = 1.75
1m + .50 + .80 = 1.75
1m + 1.30 = 1.75
1m = 1.75 - 1.30
1m = .45

cup of coffee = .40
donut = .50
carton of milk = .45

2 cartons of milk is .90 and 2 donuts is $1.00. The total equalling $1.90. $1.80 is not enough. They are short .10.