Point S is on line segment R T ‾ RT . Given R T = 3 x , RT=3x, R S = 3 x − 5 , RS=3x−5, and S T = 3 x − 1 , ST=3x−1, determine the numerical length of R T ‾ . RT .

What is the next step in the given proof? choose the most logical approach. a. statement: m 1 + m 2 + 2(m 3) = 180° reason: angle addition b. statement: m 1 + m 3 = m 2 + m 3 reason: transitive property of equality c. statement: m 1 = m 2 reason: subtraction property of equality d. statement: m 1 + m 2 = m 2 + m 3 reason: substitution property of equality e. statement: 2(m 1) = m 2 + m 3 reason: substitution property of equality