A right angle is defined as an angle whose measure is 90º.
On the other hand, two angles are congruent if their measures are the same.
Then, the reason for statement 2 is the definition of right angle.
The reason for statement 3 is the transitive property of equality (since both measures of angles F and G are equal to 90º, then the measures of the angles F and G are equal).
The reason for statement 4 is the definition of angle congruence.
