(3/4 - 1/2) * 5 = (3\4 - 2\4)*5=1\4 *5 = 5\4 = 1,25
(5/7 + 1/21) : 2 = (15\21 + 1\21) : 2 = 16\21 : 2 = 8\21
(7/10-1/5) : 3 = (7\10 - 2\10) : 3 = 5\10 : 3 = 5\30 = 1\6
(1/4-1/12) * 5 = (3\12 - 1\12) * 5 = 1\6 * 5 = 5\6
(1/4+1/6) : 10 = (3\12 + 2\12) : 10 = 5\12 : 10 = 5\120 = 1\24
( 5/6 - 1/4) :7 = (10\12 - 3\12) : 7 = 7\12 : 7 = 1\12