Nilai : 6 7 8 9 frekuensi: 10 15 p 4 nilai ratarata : 7,3 . tentukan nilai p?

Nilai rata-rata = (n1.f1 + n2.f2 + n3.f3 + n4.f4) / (n1+n2+n3+n4)
7,3 = 6.10 + 7.5 + 8.p + 9.4 / 10+5+p+4
7,3 = 60+35+36+8p / 19+p
7,3 = 131+8p / 19+p
131+8p = 7,3(19+p)
131+8p = 138,7 + 7,3p
0,7p = 7,7
p = 11

7,3 =
211,7 + 7,3p = 201 = 8p
211,7 – 201 = 8p – 7,3p
10,7 = 0,7p
= p
15,28 = p