a) 25+97-72=122-72=50
46-19+55=27+55=82
185-82+39=103+39=142
b) 72:8×56=9×56=504
9×4+36=36+36=72
28:4+15=7+15=22
c) 427+95-157-152+739=522-157-152+739=365-152+739=
=213+739=952
584+1009-274+6230=1593-274+6230=1319+6230=7549
325+183×3-136=325+549-136=874-136=738