What is m∠ABC? Justify your reasoning. Using the addition property of equality, 40 + 15 = 55, so m∠ABC = 55°. Using the subtraction property of equality, 40 − 15 = 25, so m∠ABC = 25°. Using the Angle Addition Postulate, 15 + m∠ABC = 40. So, m∠ABC = 25° using the subtraction property of equality. Using the Angle Addition Postulate, 15 + 40 = m∠ABC. So, m∠ABC = 55° after simplifying.

Using the Angle Addition Postulate, 15 + 40 = m∠ABC. So, m∠ABC = 55° after simplifying.

Step-by-step explanation:

The  Angle Addition Postulate is gotten from angles placed side by side to form a resulting angle that is the sum of all the individual angles.

If D is the interior of ABC then, ABC is split into two parts i.e ABD and DBC, then the measure of ABC is the sum of the individual two parts

m∠ABC = m∠ABD + m∠DBC.

Using the Angle Addition Postulate:

m∠ABC = m∠ABD + m∠DBC

m∠ABC = 15 + 40 = 55°

m∠ABC = 55°