2. Marta has invented a new arithmetic operation called "smile" for which she will use the symbol :). The smile is defined using the known operations of addition and multiplication by the expression

$$
a \odot b=a \cdot b+3 \cdot a+b
$$

What is $x$ if $(x \odot 5) \cdot 6=72123$?
## First solution.

First, we will write the given expression using addition and multiplication:

$x \odot 5=\mathrm{x} \cdot 5+3 \cdot x+5=8 x+5$

$(x \odot 5) \odot 6=(8 x+5) \cdot 6+3 \cdot(8 x+5)+6=(8 x+5) \cdot 9+6=72 x+51$

Now let's solve the equation $(x \odot 5) \odot 6=72123$.

$$
\begin{gathered}
72 x+51=72123 \\
72 x=72072 \\
x=72072: 72 \\
x=1001
\end{gathered}
$$