Question

The first term and last term of an arithmetic progression are -3 and 145 respectively .if the common difference is 4.(a) find the 12th term (b) find the 25th term.

Answer 1

You are told a=-3 and d = 4
so you can find any term using:
term(n) = a + (n-1)d

so term(12) = a + 11d = -3 + 11(4) = ....

find term(25) in the same way.

(the fact that the last term is 145 is not needed.
I will add the question , What term number is 145 ?

Answer 2

I think to solve this, you will be getting an equation -3+(x-1)4, solve for x and it will be your answer