Question

What property is used If m∠A = m∠B and m∠A + m∠C = m∠D, then
m∠B + m∠C = m∠D.

Answer 1

substitution property

Explanation:

You want to know the property that tells you if m∠A = m∠B and m∠A + m∠C = m∠D, then m∠B + m∠C = m∠D.

Substitution

The substitution property of equality tells you that if A = B, then B can be used in place of A in any expression.

Here, the expression using m∠A is

m∠A + m∠C = m∠D

Since m∠A = m∠B, we can put m∠B in the statement where m∠A is:

m∠B + m∠C = m∠D . . . . . . . . . substitution property

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