how do you solve the problems 2c-d=-2 and 4c+d=20 using the substitution method

Question

substitution method

Answer 1

Substitution method

Given equation 2c-d = -2

Add d to each side.

2c-d+d = -2+d

2c = -2+d

Divide by 2 to each side.

2c/2 = (-2+d)/2

c = -1+d/2 --------> (1)

Given second equation 4c+d  = 20

From (1) substiute the c value in above equaion.

4(-1+d/2)+d = 20

-4+2d +d= 20

Add 4 to each side.

-4+4+3d = 20+4

3d = 24

d = 24/3

d = 8

Substitute the d value in (1).

c = -1+8/2

c = -1+4

c = 3

Solution c = 3, d =12.

Comments

Typo mistake in last line of above solution.

Solution c = 3 and d = 8.