(c) Given, average of first three friends = 15 ⇒ Total score of first three friends = 15 x 3 = 45 Average of last three friends = 16 ⇒ Total score of last three friends = 16 x 3 = 48 Total score of four friends = 45 + 19 = 64 ∴ Score of first friend = 64 - 48 = 16 Hence, required percentage =