The answer is 120.

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Given 10 dots. Each triangle has 3 vertices. So the number of possible triangles is

${ C }_{ 3 }^{ 10 }=\frac { 10! }{ 3!7! } =\frac { 10\cdot 9\cdot 8 }{ 3\cdot 2\cdot 1 } =120$ .