Jawabanmu

2014-05-15T18:18:36+07:00
P + l = 40
p= 40-l

72 = (69.l + 74.p)/40
2880 = 69.l + 74 (40-l)
2880 = 69 l + 2960-74 l
-80 = -5l
16 = l
jadi siswa laki2 ada 16 
2014-05-15T18:24:37+07:00
p + w/ 40= 72
69
× pria + 74×wanita per 40=72
69p+74w =72×40

69p + 74w =2880  ×1
   p + w     = 40    ×74

-5p            =-80
p               =-80/-5
p               = 16