a) 2 div 3 - 2 mod 3 + 3 div 2 - 3 mod 2
= 0 - 2 + 1 - 1 = -2
b) 1/2 - 2*7 mod 2 - 8 div 4 * 4
= 1/2 - 12 mod 2 - 2 * 4
= 1/2 - 0 0 8
= 1/2 - 8
c) (12+5) mod 3 - (2*8) div 5 - 1
= 17 mod 3 - 16 div 5 - 1
= 2 - 3 - 1
= -2
d) 5/4 - 4*5 div 7 + 15 mod 3
= 5/4 - 20 div 7 + 0
= 5/4 - 2 + 0
= 5/4 - 2