#### Answer

\[x=10\]

#### Work Step by Step

The equation is \[0.7x+0.4\left( 20 \right)=0.5\left( x+20 \right)\].
Use the order of operations,
\[\begin{align}
& 0.7x+0.4\left( 20 \right)=0.5\left( x+20 \right) \\
& 0.7x+8=0.5x+10
\end{align}\]
Subtract \[0.5x\] from both sides of the equal sign,
\[\begin{align}
& 0.7x+8-0.5x=0.5x+10-0.5x \\
& 0.2x+8=10
\end{align}\]
Subtract \[8\] from both sides of the equal sign,
\[\begin{align}
& 0.2x+8-8=10-8 \\
& 0.2x=2 \\
& x=\frac{2}{0.2} \\
& x=10
\end{align}\]
Therefore, \[x=10\]