Efectuați: a (7,3-2,8):5; b 6,2+4 (18,53-4-3,24); e 2-(15,6-7,8-1,2); b 407,2+11 (57,6-2-84,9:4); d 64,8:8+3 (12,206:2-3,54), f 5 (189,7-23,6 4,5)+2 (506:11-23​