(47 х 1/26) х 13/27 -( 20 х 1/26) х 13/27

1)47  * 1/26 = 47/1*1/26 =  47/26 = 1 21/26
2) 20*1/26 = 20/1*1/26 = 20/26 = 10/13
3)1 1/26 *  13/27 = 47/26 * 13/27 = 611/702 =47/54
4)10/13  *  13/27 =130/351 =  10/27
5)47/54  -  10/27 =(47* 1  -  10 * 2)/54 = 47/54 -  20/54 =  27/54 = 1/2
ответ: 1/2