PLS IL MAKE U THE BRAINLIEST NEED HELP WITH THIS PLEASE Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles.
In the diagram below, line a and line b are parallel, line c is a transversal, and the measure of ∠ 1 is 100°.

Is ∠3 congruent to ∠ 1? On the lines below, how you determined your answer. If it is not congruent, give the correct measure of ∠ 3.

3. parallelogram

step-by-step explanation:

we turn each of our sides into direction vectors

ab=b-a=(3 - 7, 1 - 0) = (-4, 1)

bc=c-b=(1,6)

cd=d-c=(4,-1)

da=a-d=(-1,-6)

we see how the opposite sides have negated direction vectors; this is characteristic of a parallelogram.   we have congruent sides ab=cd and bc=da with unequal lengths because 1^2+6^2 is different from (-4)^2+1^2.   so it's not a square or a rhombus.  

we check the dot product of direction vectors of adjacent sides.   we have

ab dot bc = -4(1) + 1(6) = 2

that's not zero so the sides are not perpendicular.   we've ruled out rectangle.

the direction vectors indicate two pairs of congruent parallel sides, so we choose parallelogram over trapezoid.

$18 was the price of the t-shirt

step-by-step explanation:

51-50

step-by-step explanation:

10000

step-by-step explanation: divide by 2,