If m angle cap A is equal to m angle cap b and m angle cap A plus m angle cap c is equal to m angle cap d , then m angle cap b plus m angle cap c is equal to m angle cap d Which property is shown?

Since m∠A = m∠b, the measure m∠A can be replaced by m∠b in the equation m∠A + m∠C = m∠D. This gives m∠b + m∠C = m∠D, which shows the substitution property.

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