# How many integer solutions?

$x_1+x_2+x_3=28$

Find the number of integer solutions to the above equation if $$\begin{cases} 3 &\le& x_1 &\le& 9 \\ 0 &\le& x_2 &\le& 8 \\ 7 &\le& x_3 &\le& 17 \end{cases}$$.

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