Условие:

20 − (7 + 8);
30 − (6 + 5);
7 + 53;
40 − 8;
45 + 6 + 4;
59 + 7 + 3.

20 − (7 + 8) = 20 − 15 = 5
 
30 − (6 + 5) = 30 − 11 = 19
 
7 + 53 = 60
 
40 − 8 = 32
 
45 + 6 + 4 = 45 + (6 + 4) = 45 + 10 = 55
 
59 + 7 + 3 = 59 + (7 + 3) = 59 + 10 = 69