Aand \angle b∠b are vertical angles. if m\angle a=(4x+23)^{\circ}∠a=(4x+23)
∘
and m\angle b=(5x-7)^{\circ}∠b=(5x−7)
∘
, then find the measure of \angle b∠b.

m∠B=143°

Step-by-step explanation:

we know that

Vertical Angles are the angles opposite each other when two lines cross. They are always equal

so

In this problem we have that

m∠A=m∠B ----> by vertical angles

substitute the given values and solve for x

Find the measure of angle B

m∠B=(5x-7)°

substitute the value of x

m∠B=(5(30)-7)°

m∠B=143°

∠1≅∠2 by the alternate exterior angles theorem.

step-by-step explanation:

given, a ∥ b and ∠1 ≅ ∠3 .we have to prove that e ∥ f

we know that ∠1≅∠3 and that a || b because they are given. we see that by the alternate exterior angles theorem. therefore, ∠2≅∠3 by the transitive property. so, we can conclude that e || f by the converse alternate exterior angles theorem.

we have to fill the missing statement.

transitivity property states that if a = b and b = c, then a = c.

now, given ∠1≅∠3 and by transitivity property ∠2≅∠3 .

hence, to apply transitivity property one angle must be common which is not in result after applying this property which is ∠1.

the only options in which ∠1 is present are ∠1 and ∠2, ∠1 and ∠4

∠1 and ∠4 is not possible ∵ after applying transitivity we didn't get ∠4.

hence, the missing statement is ∠1≅∠2.

so, ∠1≅∠2 by the alternate exterior angles theorem.