Line segments that have the same length, or angles that have the same measure are?

The angle of a triangle are given as 6x,(x-3), and (3x+7). find x then find the measures of the angles

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)

Which of the following correctly justifies statement four of the two column proof? a. corresponding angles theorem b. transitive property of equality c. vertical angle theorem d. substitution property of equality