Lines AB
and
CD
are straight lines. Find x and y. Give reasons to justify your solutions.

x = 18

y = 54°

Step-by-step explanation:

m<MON = 90° (given)

m<MOA = 72° (given)

m<AON + m<MOA = m<MON (Angle Addition Postulate)

m<AON + 72° = 90° (Substitution)

Subtract 72° from each side

m<AON = 90° - 72°

m<AON = 18°

m<AOD = 18° + 2x

m<BOC = 3x

m<AOD = m<BOC (vertical angles)

18 + 2x = 3x (Substitution)

Subtract 2x from each side

18 = 3x - 2x

18 = x

x = 18.

72° + y + 3x = 180° (angles on a straight line)

Plug in the value of x

72 + y + 3(18) = 180

72 + y + 54 = 180

126 + y = 180

Subtract 126 from both sides

y = 54

2. angles qrt and qst both measures 156 degrees.

step-by-step explanation:  

we have been given a diagram of a circle and we are told that measure of arc qvt is 156 degrees.  

we can see from our given diagram that angle qrt and angle qst subtends to arc qvt.

since we know that angles subtended by the same arc at the circumference are always equal.

by angle subtended by same arc theorem, measure of angle qrt and angle qst will be equal to the measure of arc qvt.

therefore, angles qrt and qst both measures 156 degrees and 2nd statement is the correct choice.