Simplify the following expression x15x+20x+5x7x

The expression given is $x_{15}x+20x+5x_7x$. The notation $x_{15}x$ and $x_7x$ is ambiguous. For the purpose of simplification, I will assume that the numbers in the subscript are coefficients that multiply the variable $x$, and then are multiplied by the adjacent $x$.
Therefore, $x_{15}x$ is interpreted as $15 \cdot x \cdot x = 15x^2$.
And $5x_7x$ is interpreted as $5 \cdot 7 \cdot x \cdot x = 35x^2$.