а) 3)18+20×12
б) 2)(18+20)×12
в) 1)18×(20+12)
1) 12,918-(4,918+3,4) = (12,918-4,918)+3,4 = 8+3,4 = 11,4
2) (6,403+8,715)-2,403 = (6,403-2,403)+8,715 = 4+8,715 = 12,715
3) (13,245+9,88)-6,88 = 13,245+(9,88-6,88) = 13,245+3 = 16,245
4) 11,703-(5,4+2,703) = (11,703-2,703)-5,4 = 9-5,4 = 3,6