Question

explore the properties of angles formed by two intersecting chords.
therefore,
m∠deb + m∠aec =
2 × m∠deb.

1. by

2(mbd + mac, or
m∠bd + mac).
options: addition, substitution

m∠deb = 105°
m∠aec = 105°
mac = 130°
mbd = 80°
circle with chords intersecting at e, points a, d, b, c on circle

Explanation:

To determine the correct option for step 6, we analyze the context. We know the measures of arcs \( \widehat{AC} \) and \( \widehat{BD} \), and we are relating the angle measures to the sum of these arc measures. The substitution property is used when we replace a quantity with its equal value. Here, we are substituting the measures of the arcs (or their related angle - arc relationships) into the equation. The addition property would be about adding quantities, but here we are replacing a part of the equation with known values (the arc measures), so substitution is the correct property.

Answer:

substitution