Problems based on Numbers Test 3

Let the unit digit be x.
Ten’s digit = y ⇒ Original number = 10 y + x
New number when digits are reversed = 10x + y
According to the statement,
$10\mathit{y}+\mathit{x}+18=10\mathit{x}+\mathit{y}$
$9\mathit{y}=18=9\mathit{x}$
$\mathit{y}+2=\mathit{x}$
$2=\mathit{x}-\mathit{y}$
Let $\mathit{x}=3$ and $\mathit{y}=1$
Prime number 13, 31.
When $\mathit{x}=9,\mathit{y}=7$.
Prime numbers are 79, 97.
There are two possible numbers.