Theo đề, ta có:
\(\left\{{}\begin{matrix}a-b=16.8\\a+1.4=3\left(b+1.4\right)\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a-b=16.8\\a-3b=2.8\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2b=14\\a-b=16.8\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}b=7\\a=23.8\end{matrix}\right.\)