The correct answer is Choice A.
Use the formula for the area of a triangle to form an equation. Then solve the equation to find $x$.
Since the negative value cannot be a dimension of the triangle, $x=7$.
Choice B is incorrect because the area of a triangle with base length 10 and height 13 is 65.
Choice C is incorrect because the area of a triangle with base length 17 and height 20 is 170.
Choice D is incorrect because the area of a triangle with base length 35 and height 38 is 665.
✨ Expert's Tip ✨
A measurement, such as a length, weight, speed, height, and time cannot be a negative value.