1) 5/12 : 3/10 =5/12 *10/3 =(5*10)/(12*3) =(5*5)/(6*3) =(25/18) =1 7/18(одна целая семь восемнадцатых)
2) 1/4 -2 2/3 =1/4 -8/3 =(3 -4*8)/12 =(3 -32)/12 =29/12 =2 5/12
3) 7 1/2 *1/3 =15/2 *1/3 =15/6 =2 1/2 =2.5
4) =7/24 *8/3 =(7*8)/(24*3) =7/(3*3) =7/9