428. Амалдарды орындаңдар: 1) 11/20 + (−2 11/15); 2) −2/5 + 6 3/4; 3) −7/12 + 5 1/16; 4) 5/12 + (−4/15).

1. \(\frac{11}{20}-2\frac{11}{15}=\frac{33}{60}-\frac{164}{60}=-\frac{131}{60}=-2\frac{11}{60}\).
2. \(-\frac{2}{5}+6\frac{3}{4}=-\frac{8}{20}+\frac{135}{20}=\frac{127}{20}=6\frac{7}{20}\).
3. \(-\frac{7}{12}+5\frac{1}{16}=-\frac{28}{48}+\frac{243}{48}=\frac{215}{48}=4\frac{23}{48}\).
4. \(\frac{5}{12}-\frac{4}{15}=\frac{25-16}{60}=\frac{9}{60}=\frac{3}{20}\).

Жауабы: 1) −2 11/60; 2) 6 7/20; 3) 4 23/48; 4) 3/20.