. này là nhân hay phẩy vậy bạn
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\(\frac{3}{7}\div x-\frac{2}{5}=0,2\)
\(\frac{3}{7}\div x-\frac{2}{5}=\frac{1}{5}\)
\(\frac{3}{7}\div x=\frac{1}{5}+\frac{2}{5}\)
\(\frac{3}{7}\div x=\frac{3}{5}\)
\(x=\frac{3}{7}\div\frac{3}{5}\)
\(x=\frac{7}{5}\)
3/7:x-2/5=0,2
3/7:x 2/5=2/10
3/7:x =2/10+2/5
3/7:x =6/10=3/5
x =3/7:3/5
x =15/21=5/7