use formula an = a+( n -1)d
where , a = first term
n = number of terms
d = common difference
Here , a = 12 , let's suppose n = N and d = 14-12=2
so, an = 12 + ( N -1)2
an = 12+2N - 2
an = 2N +10
an = 2(N+5) is the equation for the nth term of arithmetic sequence of 12 , 14 , 16, 18-------
