Question

Insert five arithmetic means between 7 and 17.

Answer 1

so you have 7 terms with a=7 and
a + 6d = 17
7 + 6d = 17
d = 10/6 = 5/3

form the missing terms,
e.g term(2) = 7 + 5/3 = 26/3
term(3) = 26/3 + 5/3 = 31/3
etc