bạn ơi sao 15.4 bằng 20 ạ

\(\Rightarrow33+x=71-26\)

\(\Rightarrow33+x=45\)

\(\Rightarrow x=45-33\)

\(\Rightarrow x=12\)

\(5x=245-5\)

\(5x=240\)

\(x=240\div5\)

\(x=48\)

\(\Leftrightarrow2.x=120\div10\)

\(\Leftrightarrow2.x=12\)

\(\Leftrightarrow x=12\div2\)

\(\Leftrightarrow x=6\)

\(5\left(x-9\right)=350\)

\(x-9=350\div5\)

\(x-9=70\)

\(x=70+9\)

\(x=79\)