А) (1 - 1/2) : (1/2 - 1/3) = 3
1) 1 - 1/2 = 2/2 - 1/2 = 1/2
2) 1/2 - 1/3 = 3/6 - 2/6 = 1/6
3) 1/2 : 1/6 = 1/2 * 6/1 = 6/2 = 3
б) (1/2 + 1/4 - 2/5) : 4/5 = 7/16
1) 1/2 + 1/4 = 2/4 + 1/4 = 3/4
2) 3/4 - 2/5 = 15/20 - 8/20 = 7/20
3) 7/20 : 4/5 = 7/20 * 5/4 = (7*1)/(4*4) = 7/16