The answer is <span>angle addition postulate proof </span><span>mTRV + mTRS = 180°, both angles are called supplementary angles, their sum is 180°</span>
The Angle addition Postulate :The postulate describes that putting two angles side by side with their vertices together creates a new angle whose measure equals the sum of the measures of the two original angles.Given the sum of a pair of angles and the algebraic expressions that represent them we can form and solve an equation.
It is given mTRV = 60° mTRS = (4x)° Prove: x = 30'
In statement 3 we have m<TRS+M<TRV=180(The angles add to given 180)
The missing reason in step 3 is angle addition postulate.
