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

Question

substitution method

Answer 1

line 1: 2c-d=-2

line 2: 4c+d=20

line1 +line2...6c=18

c=3

line 1...6-d=-2, so d=6+2

d=8

Answer 2

2c-d=-2

4c+d=20

taking the equation 2c-d=-2 make d the subject of the formula which is

d=2c+2

substitute d with the above equatio in the second equation 4c+d=20 then you will get

4c+2c+2=20 then solve thie equation and get

6c+2=20 subtract 2 both sides in this equation and get 6c=18 and divide by 6 both sides and get

c=3

take the first equation 2c-d=-2 and substitute c with 3 like this 2*3-d=-2 and get 6-d=-2 and find d

subtract 6 both sides and  remain with -d=-8 and divide by -1 both sides and get d=8