One winter, a group of students measured snowfall totals at their school. This chart shows how many inches of snow the students measured each month How much total snowfall did they receive at their school that winter? month. snowfall
December 4.2
January. 8.9
February. 5.4​

Here is their argument. given the obtuse angle x, we make a quadrilateral abcd with ∠dab = x, and ∠abc = 90◦, and ad = bc. say the perpendicular bisector to dc meets the perpendicular bisector to ab at p. then pa = pb and pc = pd. so the triangles pad and pbc have equal sides and are congruent. thus ∠pad = ∠pbc. but pab is isosceles, hence ∠pab = ∠pba. subtracting, gives x = ∠pad−∠pab = ∠pbc −∠pba = 90◦. this is a preposterous conclusion – just where is the mistake in the "proof" and why does the argument break down there?

If the measure of xyz is 81 what is the measure of yz

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.