28 * 3 − 57 = (20 + 8) * 3 − 57 = 20 * 3 + 8 * 3 − 57 = 60 + 24 − 57 = 84 − 57 = 27
 
34 + 13 * 5 = 34 + (10 + 3) * 5 = 34 + (10 * 5 + 3 * 5) = 34 + 50 + 15 = 84 + 15 = 99
 
98 − 23 * 4 + 24 = 98 − (20 + 3) * 4 + 24 = 98 − (20 * 4 + 3 * 4) + 24 = 98 − (80 + 12) + 24 = 98 − 92 + 24 = 6 + 24 = 30
 
28 * 2 − 13 * 4 = (20 + 8) * 2 − (10 + 3) * 4 = (20 * 2 + 8 * 2) − (10 * 4 + 3 * 4) = (40 + 16) − (40 + 12) = 56 − 52 = 4
 
(49 + 28) : 7 = 49 : 7 + 28 : 7 = 7 + 4 = 11
 
(64 + 24) : 4 = 88 : 4 = (80 + 8) : 4 = 80 : 4 + 8 : 4 = 20 + 2 = 22