Berapa rata rata nya... Plis buat besok pagi

jawab
n1 = banyak  L = 21
x1 = rata L = 76
n2 = banyak P = 14
x2= rata P =
xg = rata  gabungan = 78

(n1 +n2) xg = n1. x1 + n2. x2
(21+14) 78 = 21 (76) + 14(P)
(35) 78 = 21 (76) - 14P
14 p =35 x78 - 21 x 76
14 p = 2.730 - 1596 = 1.134
p = 81