Tính phép tính. a) 3/4 + 2/5 - 7 / 10 + 13/ 20

a) \(\frac{3}{4} + \frac{2}{5} - \frac{7}{{10}} + \frac{{13}}{{20}} = \frac{{3 \times 5}}{{20}} + \frac{{2 \times 4}}{{20}} - \frac{{7 \times 2}}{{20}} + \frac{{13}}{{20}} = \frac{{15 + 8 - 14 + 13}}{{20}} = \frac{{22}}{{20}} = \frac{{11}}{{10}}\)

b) \(\frac{5}{7} \times \frac{4}{3} + \frac{6}{5} \times \frac{5}{7} = \frac{5}{7} \times \left( {\frac{4}{3} + \frac{6}{5}} \right) = \frac{5}{7} \times \left( {\frac{{20 + 18}}{{15}}} \right) = \frac{5}{7} \times \frac{{38}}{{15}} = \frac{{38}}{{21}}\)

c) 12,45 + 34,5 – 3,46 $\times$ 3 = 46,95 – 10,38 = 36,57

d) (2,34 + 0,87 – 1,5) $\times$ 6 + 9,756 = 1,71 $\times$ 6 + 9,765 = 10,26 + 9,765 = 20,025