arithmetic
posted by payal .
4th &7th term is 20 & 32 , find a ,d & nth

Assuming you are working with arithmetic sequences,
term(4) = a+3d = 20
term(7) = a+6d = 32
subtract the two equations:
3d = 12
d = 4
sub back into either top equation to find a
term(n) = a + (n1)d