A triangle has one side that measures 9 units, another side that measures x, and a third side that measures 2 units. Which equation would we use to find the value of x? A) x + x + 2 = 29 B) x + x + 2 + 9 = 29 C) x + x + x + 2 = 29 D) x+x+x + 2+9=29

None of the suggested answers makes any sense.

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It looks like you may be trying to write an equation for the perimeter. Such an equation might be
  9 + x + 2 = p
where p is used to represent the perimeter.
If the figure is truly a triangle, the value of x will be between 9-2=7 and 9+2=11. Thus, the perimeter can be no less than 18 and no more than 22. In any event, the value of x will show up only once in the equation for the perimeter.

If the perimeter is 19 (a value between 18 and 22), an equation that might be used to find x would be
  x + 2 + 9 = 19