1) 2 1/6 - 1 2/3 = 2 1/6 - 1 4/6 = (2*6+1)/6 - (1*6+4)/6 = 13/6 - 10/6 = 3/6=1/2
2) 7:(2 1/3) + 9:(2 1/4) = 7:((2*3+1)/3) + 9:((2*4+1)/4) = 7:(7/3) + 9:(9/4) = 3+4 = 7
3) 3 1/2 + 2.5*16 = 3.5 + 40 = 43.5
4) -(-2.4/0.6) = -(-4) = 4
5) 5% = 0.05, 20%=0.2, 0.05*0.2 = 0.01 = 1%, 120%*10 = 120/100*10 = 12.
М.б. сначала 5% от числа 20?