The 7th and 12th term of an arithmetic progression are -15 and 5 respectively. What is the 16th term?

Answer: Option C

T₇ = a + 6d = -15 ....... (1)
T₁₂ = a + 11d = 5 ...... (2)
on solving (1) and (2)
d = 4 & a = -39
T₁₆ = a + 15d
      = -39 + 15(4)
      = -39 + 60
      = 21