Выполните действия: а)2 1/4 - 1 1/2; б 3 4/7 + 1 2/3

Вычислим значения выражений: 

а) 2 1/4 - 1 1/2 = 2 + 1/4 - 1 - 1/2 = (2 - 1) + (1/4 - 1/2) = 1 + 1/4 - 1/2 = 4/4 + 1/4 - 1/2 = (4 * 1 + 1 * 1 - 1 * 2)/4 = (4 + 1 - 2)/4 = (5 - 2)/4 = 3/4; 

б) 3 4/7 + 1 2/3 = 3 + 4/7 + 1 + 2/3 = (3 + 1) + (4/7 + 2/3) = 4 + 4/7 + 2/3 = 4 + (4 * 3 + 2 * 7)/21 = 4 + (12 + 14)/21 = 4 + 26/21 = 4 + 21/21 + 5/21 = 4 + 1 + 5/21 = 5 + 5/21 = 5 5/21.