Упростите:2/7(1,4a-3целых1/2в)-1,2(5/6a-0,5в)
........=2/7 * 7/5 а - 2/7 * 7/2 b - 6/5 * 5/6 a+1.2*0.5b=2/5 a - b - a+0.6b=0.4a-a-b+0.6b= - 0.6a - 0.4b