Prove: the sum of the interior angle measures of labc is 180°,
statement
reason
1. let points a, b, and cform a
triangle
given
2. let de be a line passing
through b, parallel to ac,
with angles as labeled
defining a parallel line and labeling angles
4. m21 = m24, and
m23 = m25.
congruent angles have equal measures.
5. m24+ m22 - m25 = 180°
angle addition and definition of a straight angle
6. m21 - m42 - m23 = 180°
substitution
what is the missing step in this proof?

Kevin has a spinner that has 10 equal sections and 2 sections of each color—red, blue, green, yellow, and purple. kevin spins the spinner 180 times. kevin determines about how many times the spinner will land on red or green, and his work is shown below. -kevin has the formula reversed; it should be the total number of sections over the number of red or green sections. -kevin should have used a 4 in the numerator because there are 2 red sections and 2 green sections. -kevin should multiply by the number of sections in the spinner rather than the total number of spins. -kevin calculated the prediction correctly and did not make any mistakes.