Thực hiện phép tính: a) (15,25 + 3,75).4 + (20,71 + 5,29).5; b) $$\frac{4} + \frac + \frac{6} + \frac{{ - 3}}{5} + \frac{2} + \frac{{ - 10}} + \frac{3}$$ ; c) $$\frac{5}.\frac{5}{7} + \frac{5}.\frac{2}{7} + \frac{6};$$ d) $\left( { - \frac{5} + 0,75 + \frac{7}} \right):\left( { - 2\frac{1}{8}} \right)$.