The value of x for which 2x, (x+10) and (3x+2) are . . .

Question : The value of x for which 2x, (x+10) and (3x+2) are the three consecutive terms of the an AP, is 

a) 6

b) -6

c) 18

d) -18

Doubt by Ziya

Solution :
2x, (x+10) and (3x+2) are in AP
a₁ = 2x

a₂ = x+10

a₃ = 3x+2

Terms are in AP
∴ d₁=d₂

a₂-a₁=a₃-a₂

x+10-2x=3x+2-(x+10)
-x+10=3x+2-x-10

-x+10=2x-8

-x-2x=-8-10

-3x=-18

3x=18

x=18/3

x=6

Hence, 'a) 6' would be the correct option.