a)
25 div 3 = 24:3=8
73 div 7 = 70:7= 10
31 div 7 = 28:7= 4
25 mod 3= 25-24=1
73 mod 7 = 73-70=3
31 mod 7 = 31-28=3
b)
2 div 3 + 1 = 0+1=1
17 - 23 div 7 = 17 - 3 = 14
31 div (7+5) = 31 div 12 = 2
25 mod 3 + 25 div 3 = 8+1=9
47 div (3 mod 7) = 47 div 3 = 15
31 mod (7 div 2) = 31 mod 3 = 1