Mình làm cách lớp 6 nha bạn, cách lớp 4 mình không biết.
\(\frac{1}{2}.x+\frac{1}{5}.x=\frac{2}{5}\)
\(\Rightarrow x.\left(\frac{1}{2}+\frac{1}{5}\right)=\frac{2}{5}\)
\(\Rightarrow x.\frac{7}{10}=\frac{2}{5}\)
Giờ thành tìm x rồi!
\(x=\frac{7.5}{2.10}\)
\(x=1\frac{3}{4}\)
Xong!
\(\frac{1}{2}\times x+\frac{1}{5}\times x=\frac{2}{5}\)
\(x\times\left(\frac{1}{2}+\frac{1}{5}\right)=\frac{2}{5}\)
\(x\times\frac{7}{10}=\frac{2}{5}\)
\(x=\frac{2}{5}:\frac{7}{10}\)
\(x=\frac{4}{7}\)
\(\frac{1}{2}\times x+\frac{1}{5}\times x=\frac{2}{5}\)
\(\Rightarrow\left(\frac{1}{2}+\frac{1}{5}\right)\times x=\frac{2}{5}\)
\(\frac{7}{10}\times x=\frac{2}{5}\)
\(x=\frac{2}{5}:\frac{7}{10}\)
\(x=\frac{4}{7}\)
\(\frac{1}{2}\times x+\frac{1}{5}\times=\frac{2}{5}\)
\(\left(\frac{1}{2}+\frac{1}{5}\right)\times x=\frac{2}{5}\)
\(\frac{7}{10}\times x=\frac{2}{5}\)
\(x=\frac{2}{5}:\frac{7}{10}\)
\(x=\frac{4}{7}\)
