Tính bằng cách thuận tiện a) 524 × 63 + 524 × 37 – 2 400

a) 524 × 63 + 524 × 37 – 2 400

= 524 × (63 + 37) – 2 400

= 524 × 100 – 2 400

= 52 400 – 2 400

= 50 000

b) \(\frac{7}{9}\, \times \,\,\frac{6}{5}\,\, + \,\,\frac{6}{5}\, \times \,\,\frac{2}{9}\,\, + \,\,\frac{4}{5}\)

\( = \left( {\frac{7}{9} + \frac{2}{9}} \right) \times \frac{6}{5} + \frac{4}{5}\)

\( = \frac{6}{5} + \frac{4}{5}\)

\( = \frac{{10}}{5}\) = 2