Answer :
We will use the following variables :
g for glazed
f for cream filled donuts
c for chocolate donuts
So, the equation for combo 1
3 g + 4 f + 5 c = $38
The equation for combo 2:
5 g + 6 f + c = $32
The equation for combo 3:
4 g + 4 f + 4 c = $36
So, the system of equations are:
3 g + 4 f + 5 c = 38 (1)
5 g + 6 f + c = 32 (2)
4 g + 4 f + 4 c = 36 (3)
B) Now, we need to solve the system of equations:
From equation 3:
4 g + 4 f + 4c = 36
divide all terms by 4
So, g + f + c = 9
Solve for c:
c = 9 - g - f
Substitute with the value of c at the equations (1)
At (1):
3 g + 4 f + 5 (9 - g - f) = 38
3g + 4f + 45 - 5g - 5f = 38
-2g - f = 38 - 45
-2g - f = -7
Multiply all terms by -1
2g + f = 7
Solve for f
f = 7 - 2g
Substitute with f at the equation of c
c = 9 - g - (7 - 2g)
c = 9 - g - 7 + 2g
c = g + 2
So, we have reached to :
f = 7 - 2g and c = g + 2
substitute with f and c at the equation (2)
5g + 6f + c = 32
5g + 6 (7 - 2g) + g + 2 = 32
solve for g
5g + 42 - 12 g + g + 2 = 32
5g - 12g + g = 32 - 42 - 2
-6g = -12
Divide both sides by -2
g = -12/-6 = 2
f = 7 - 2g = 7 - 2 * 2 = 7 - 4 = 3
c = g + 2 = 2 + 2 = 4
So, the cost of glazed = $2
The cost of cream filled = $3
The cost of chocolate = $4
