80 + 20 : 4 * 2 = 90
60 * (9 − 6 : 3) = 420
15 * 4 : 3 = 20
96 : 24 * 9 = 36

Проверка:
$80 \overset{3}{+} 20 \overset{1}{:} 4 \overset{2}{*} 2 = 90$
1) 20 : 4 = 5
2) 5 * 2 = 10
3) 80 + 10 = 90
 
$60 \overset{3}{*} (9 \overset{2}{-} 6 \overset{1}{:} 3) = 420$
1) 6 : 3 = 2
2) 9 − 2 = 7
3) 60 * 7 = 420
 
$15 \overset{1}{*} 4 \overset{2}{:} 3 = 20$
1) 15 * 4 = (10 + 5) * 4 = 10 * 4 + 5 * 4 = 40 + 20 = 60
2) 60 : 3 = 20
 
$96 \overset{1}{:} 24 \overset{2}{*} 9 = 36$
1) 96 : 24 = 4
2) 4 * 9 = 36