a. (15 + 37) + (52 - 37 – 17)
=15+37+52-37-17
=50
b. (38 – 42 + 14) – (25 – 27 – 15)
=38-42+14-25+27+15
=27
c. -(21 – 32) – (-12 + 32)
=-21+32+12-32
=-9
d. -(12 + 21 – 23) - (23 – 21 + 10)
=-12-21+23-23+21-10
=-22
e. (57 – 725) – (605 – 53)
=57-725-605+53
=-1220
f. (55 + 45 + 15) – (15 – 55 + 45)
=55+45+15-15+55-45
=110