137. The number of correct non-negative integer solutions of the equation $x_1 + x_2 + x_3 = \dfrac{10}{x_4}$ is which of the following? (1) $60$ (2) $72$ (3) $81$ (4) $96$
\textbf{137.} The number of correct non-negative integer solutions of the equation $x_1 + x_2 + x_3 = \dfrac{10}{x_4}$ is which of the following?
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(1) $60$ \hfill (2) $72$ \hfill (3) $81$ \hfill (4) $96$
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