Question

if a = 12, d= 4,Tn = 76,find n

Answer 1

I think it may be 17
76=12+(n-1)4
76=12+4n-4
76=8+4n
68=4n
hence n=17

Answer 2

tn=a+(n-1)d

substituting all given information

76=12+(n-1)4

76=12+4n-4

76=8+4n

76-8=4n

68=4n

68/4=n

n=17