Final answer:
Sharon likely used the angle sum property of a triangle, which states that the sum of the angles in a triangle is 180 degrees, to solve for x by subtracting the known angles from 180. Therefore the correct option a) Angle sum property of a triangle
Step-by-step explanation:
The statement that best justifies Sharon's answer that x=70 is the angle sum property of a triangle. According to this property, the sum of the angles in any triangle is 180 degrees. For a given triangle, if you know the measures of two angles, you can find the third angle by subtracting the sum of the two known angles from 180 degrees.
As a generic example, if a triangle has angles A, B, and C, then A + B + C = 180 degrees. If A = 50 degrees and B = 60 degrees, then C can be calculated as C = 180 - 50 - 60 = 70 degrees. The same property would apply to Sharon's triangle to solve for x.
Sharon's answer can best be justified using the Angle sum property of a triangle. According to this property, the sum of the angles in any triangle is always 180 degrees. Since Sharon has determined that x is equal to 70 degrees, we can calculate the other angles in the triangle by subtracting 70 from 180. This will ensure that the sum of all three angles equals 180 degrees.
Therefore the correct option a) Angle sum property of a triangle