Ta có: a : 7 = 3 (dư 9)

=> a = 3.7 + 9

a = 30

Vậy ...

a = 30

:)

nice

Nice

Chuyển coin ý hả bạn? (sai cho mik xl)

\(\frac{84}{48}=\frac{84:12}{48:12}=\frac74\)

\(\frac12+\frac14+\frac18+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)

\(=\frac{32}{64}+\frac{16}{64}+\frac{8}{64}+\frac{4}{16}+\frac{2}{64}+\frac{1}{64}\)

\(=\frac{63}{64}\)

2 tháng rưỡi bằng 45 ngày

\(\left(1-\frac25\right)\times\left(1-\frac27\right)\times\left(1-\frac29\right)\times\ldots\times\left(1-\frac{2}{97}\right)\times\left(1-\frac{2}{99}\right)\)

\(=\frac35\times\frac57\times\frac79\times\ldots\times\frac{95}{97}\times\frac{97}{99}\)

\(=\frac{3\times5\times7\times\ldots\times95\times97}{5\times7\times9\times\ldots\times97\times99}\)

\(=\frac{3}{99}=\frac{1}{33}\)