nilai rata-rata ujian tersebut

Rata2 = [(60 × 40) + (70 × 20) + (80 × 30) + (90 × 20) + (100 × k)] ÷ (110 + k)
76 = (2400 + 1400 + 2400 + 1800 + 100k) ÷ (110 + k)
76 (110 + k) = 8000 + 100k
8360 + 76k = 8000 + 100k
360 = 24k
k = 15

60(40)+ 70(20)+80(30)+90(20)+100(k) ÷ 40+20+30+20+k =76
2400+1400+2400+1800+100k ÷ 90+k=76
8000+100k÷110+k=76
8000+100k= 8360+76k
24k=360
k= 15