3 (x + 4) = 18 (Given)

3x + 12 = 18 (Distributive Property)

3x = 6 (Subtraction)

x = 2

Give a reason for the last step in the argument shown.

GivEn - 3 (x+4) = 18

(when we expand it using Distributive property) - 3x+12=18

(and when we change the side of 12 and subtract it from 18, it becomes) - 3x=6

and then we have to change the side of 3 and bring it to RHS and as it is multiplied with x in the the LHS, in RHS it will be divided with 6 in RHS, thus it will form the equation = x=6/3, which when simplified becomes, 2. Thus, our answer is 2.