Fm∠a = m∠b and m∠a + m∠c = ∠d, then m∠b + m∠c = ∠d. which property is shown

It is the property of "Substitution property of Equality".

Step-by-step explanation:

Since we have given that

m∠A = m∠B (1)

and

m∠A + m∠C = ∠D (2)

We will put the equation (1) in equation (2), we get that

m∠B + m∠C = ∠D

It is the property of "Substitution property of Equality":

In this property, if we have two values which are congruent, then we put the value of one value in other equation by substituting in place of one value.

Hence, it is the property of "Substitution property of Equality".

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step-by-step explanation:

at least i think its