It looks like you have an equation involving variables \( x \) and \( y \), but the equation is not entirely clear due to the formatting. Let's try to interpret it correctly.

If the equation is meant to be:
\[ x \cdot yx.y = 21 \]

This can be interpreted in a couple of ways. One possible interpretation is that \( yx.y \) represents a number where \( y \) is concatenated with \( x \) and then a decimal point followed by \( y \). For example, if \( x = 3 \) and \( y = 2 \), then \( yx.y \) would be \( 23.2 \).

However, this interpretation seems unusual for a mathematical equation. Another possibility is that there might be a typo or formatting issue.

To proceed, let's clarify the equation. If you meant:
\[ x \cdot y \cdot x \cdot y = 21 \]
or
\[ x \cdot y \cdot y = 21 \]

Please provide more context or correct the equation if possible. If you have specific values for \( x \) and \( y \), or additional constraints, that would also help in solving the equation.