(8 7/15- 3 3/4+ 4 2/5- 8 7/60):4 1/4-2 3/4)=

1)
$8 \frac{7}{15} - 3 \frac{3}{4} = 8 \frac{28}{60} - 3 \frac{45}{60} = 7 \frac{88}{60} - 3 \frac{45}{60} = 4 \frac{43}{60}$
2)
$4 \frac{43}{60} + 4 \frac{2}{5} = 4 \frac{43}{60} + 4 \frac{24}{60} = 8 \frac{67}{60} = 8 + 1 \frac{7}{60} = 9 \frac{7}{60}$
3)
$9 \frac{7}{60} - 8 \frac{7}{60 } = 1$
4)
$4 \frac{1}{4} - 2 \frac{3}{4} = 3 \frac{5}{4} - 2 \frac{3}{4} = 1 \frac{2}{4} = 1 \frac{1}{2}$
5)
$1 \div 1 \frac{1}{2} = 1 \div \frac{3}{2} = 1 \times \frac{2}{3} = \frac{2}{3}$
Ответ:
$\frac{2}{3}$