how to solve a=7a+(n-3)d for d ?

Question

how to solve a=7a+(n-3)d for d

Answer 1

a = 7a + (n - 3)d                   Given

a - 7a = 7a + (n - 3)d - 7a      Subtract 7a from each side

-6a = (n - 3)d                        Simplify each side

-6a/(n -3) = (n - 3)d/(n -3)     Divide each side by n - 3

-6a/(n - 3) = d                       Simplify the right side

d = -6a/(n - 3)                        Symmetric Property

d = -6a/(n - 3) * (-1/-1)          Multiply the right side by -1/-1

d = 6a/(-n + 3)                       Simplify

d = 6a/(3 - n)                         Commutative property of addition