Question

in an arithmetic progression given n is equal to 4 d is equal to 2 s n is equal to minus 14 then find n and a

Answer 1

-14 = 4/2(2a + 3*2)

-7 = 2a + 6

so a = -13/2

its acc. to what is given , plz give proper information with gap for correct answer if this is wrong