I WILL AWARD BRAINLIEST Given: AC = AB, CD = DE

m∠ABC = 70°, m∠ ECB = 35°

Prove: DE ║BC

m∠ACB = m∠, By reason ( Base angles theorem, Exterior Angle theorem, Supplementary angles, Vertical Angles theorem ) - choose one

a) By Base angle theorem

b)DE||BC since and they are alternate interior angles

Step-by-step explanation:

Given: AC = AB, CD = DE

∠ABC = 70°, m∠ ECB = 35°

Refer the attached figure

AB = AC

So, By Base angle theorem : if the sides of a triangle are congruent then the angles opposite these sides are congruent.

So,

So,      ----1

CD = DE

So, by Base theorem

Let  be x

So,

Using 1

70 = x+35

35=x

Now

So, DE||BC since and they are alternate interior angles

i believe it's a.

i'm not sure on this one, most likely correct.

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.