( 3 целых 3/4 + 12/13) + 1 целая 5/14+(4 целых 1/3+2 целых 1/4)

(3 3/4 + 12/13) + 1 5/14 + (4 1/3 + 2 1/4) = 12 25/28;

1). 3 3/4 + 12/13 = 15/4 + 12/13 = 195/42 + 48/42 = (195 + 48)/42 = 243/42 = 5 33/42;

2). 4 1/3 + 2 1/4 = 13/3 + 9/4 = 42/12 + 27/12 = (42 + 27)/12 = 69/12 = 23/4 = 5 3/4;

3). 5 33/42 + 1 5/14 = 243/42 + 19/14 = 243/42 + 57/42 = (243 + 57)/42 = 300/42 = 7 6/42 = 

= 7 1/7;

4). 7 1/7 + 5 3/4 = 50/7 + 23/4 = 200/28 + 161/28 = (200 + 161)/28 = 361/28 = 12 25/28;