Total = Average × Number of pupils.<br><br>&bull; Total marks of 4 pupils = 67.5 × 4 = 270<br>&bull; Troy + Olivier = 80 + 70 = 150<br>&bull; John + Mickey = 270 − 150 = 120<br>&bull; Since John = Mickey, each = 120 ÷ 2 = 60<br><br>Final Answer: 60