3)8,56•9,2-85,3•9,2=
4)7,12•13,9-7,12•3,4=

8,56•9,2-85,3•9,2 = 9,2 (8,56 - 85,3)= 9,2 * (-76,74) = -706,0087,12•13,9-7,12•3,4 = 7,12 (13,9 - 3,4) = 7,12 * 10,5 = 74,76