Three consecutive terms of an arithmetic progression are 20 - x, 18, -44 + 7x. What is
the common difference of the progression?

8

Step-by-step explanation:

Common difference = 2nd term - first term

                                  = 18 - [20 - x] = 18 - 20 +x  = -2 + x

Common difference = third term - 2nd term

                                 = -44 + 7x - 18 = -62 + 7x

7x - 62 = -2 +x

7x - x = -2 +62

6x = 60

x = 60/6

x = 10

First term = 20-x = 20-10 = 10

Common difference  =  18 - 10 = 8

Check:

Third term = second term + 8 = 18 + 8 = 26

Third term = -44 + 7x

                 = -44 + 7*10 {x =10}

                 = -44 + 70 = 26

x=10

Step-by-step explanation:

hello :

the common difference is : (-44+7x)-18 =18-(20-x)

-44+7x-18 = 18-20+x

7x-x = 18-20+18+44

6x = 60

x=60/6 =10