Iwill mark as what is the length of side bc of the triangle?

BC = 24

Step-by-step explanation:

since ABC is an isosceles triangle

<C = <B,  then AC = AB

AC=AB

x+8 = 2x-1

subtract x from each side

x+8-x =2x-1-x

8 =x-1

add 1 to each side

8+1 = x-1+1

9 =x

BC = 3x-3

BC = 3(9) -3

BC= 27-3

BC = 24

answer: as the alternate interior angles are congruent, the opposite

sides of quadrilateral abcd are parallel.

step-by-step explanation:

so, the missing phrase in elba's proof is: alternate

interior angles

let's break this statement up so we can find the answer:

by cpctc, angle abd is equal to angle cdb and angle adb is

equal to angle cbd.

since

angle abd is equal to angle cdb, this means that they are alternate interior angles

so, the correct answer would be: as the alternate interior angles are congruent, the opposite

sides of quadrilateral abcd are parallel.

two interior angles which lie on opposite sides of a

transversal   and on different parallel

lines and are called alternate interior angles.