Question

Use the elimination method to solve each linear system.

1) 2x-9y=-55 and x+2y=18

2) 3x+2y=7 and 6x-6y=-6

3) 6x+10y=2 and 7x+4y=-13

4) 3x+2y=5 and x-2y=-1


Abby mixes cinnamon and nutmeg to make 25g of a spice mix. Cinnamon costs 9 cents per gram, and nutmeg costs 12.5 cent per gram. The spice mix costs 9.7 cents per gram. How much of each spice does Abby need to use?

Answer 1

1) x=4, y=7

2) x=1, y=2

3) x=-3, y=2

4) x=1, y=1

word problem) 5g of nutmeg and 20g of cinnamon

Explanation:

1)

2x-9y=-55

2(x+2y) = 2x+4y = 36

(2x+4y)-(2x-9y)=36-(-55)

13y = 91

y = 7 so x = 4

2)

2(3x+2y) = 6x+4y = 14

6x-6y=-6

(6x+4y)-(6x-6y) = 14-(-6)

10y = 20

y = 2 so x = 1

3)

2(6x+10y) = 12x+20y = 4

5(7x+4y) = 35x+20y = -65

(35x+20y) - (12x+20y) = -65-4

23x = -69

x = -3 so y = 2

4)

just add them

(3x+2y)+(x-2y) = 5+(-1)

4x = 4

x = 1 so y= 1

last)

c+n = 25

9c + 12.5n = 25*9.7 = 242.5

9(c+n) = 9*25

9c+9n=225

9c+12.5n - 9c-9n = 242.5-225

3.5n = 17.5

n = 5 so c = 20

5g of nutmeg and 20g of cinnamon