a) {[271*3-105*7]*9-340:2}:2 =
{[813-735]*9-170}:2 =
{78*9-170}:2 =
{702-170}:2 = 532:2 = 266
b) {[(120:6*10:5+60):10+590]-300}-102 =
{[(20*10:5+60):10+590]-300}-102 =
{[(200:5+60):10+590]-300}-102=
{[(40+60):10+590]-300}-102 =
{[100:10+590]-300}-102 =
{600-300}-102 = 300-102 = 198