/ -ЭТО ДРОБЬ а) 5/6-3/4; б )1/3+1/5; в)3/10+1/2; г) 1/3-1/7; д)

Для того чтобы делать убавку, 5/6 обязаны помножить на 4/4, а 3/4 на 6/6. После этого делаем убавку.

а) 5/6 - 3/4 = 5/6 * 4/4 - 3/4 * 6/6 = 20/24 - 18/24 = 2/24 : 2/2 = 1/12;

б ) 1/3 + 1/5 = 1/3 * 5/5 + 1/5 * 3/3 = 5/15 + 3/15 = 8/15;

в) 3/10 + 1/2 = 3/10 + 1/2 * 5/5 = 3/10 + 5/10 = 8/10 : 2/2 = 4/5;

г) 1/3 - 1/7 = 1/3 * 7/7 - 1/7 * 3/3 = 7/21 - 3/21 = 4/21;

д) 2/9 + 0 = 2/9;

е) 9/20 + 3/8 = 9/20 * 2/2 + 3/8 * 5/5 = 18/40 + 15/40 = 33/40;

ж) 19 - 11/50 = 19 * 50/50 - 11/50 = 950/50 - 11/50 =939/50 = 18,78;

з) 13/50 -  17/75 = 13/50 * 3/3 - 17/75 *2/2 = 39/150 - 34/150 = 5/150 : 5/5 = 1/30;

и) 11/14 + 8/21 = 11/14 * 3/3 + 8/21 * 2/2 = 33/42 + 16/42 =49/42 = 1,17;

к) 7/15 - 0 = 7/15;