The mean temperature for the first 4 days in january was -2°c. the mean temperature for the first 5 days in january was -4°c. what was the temperature on the 5th day?

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?

What is the effect on the graph of the function f(x)=x when f(x) is replaced with -f(x)+4

Qrst is a parallelogram. determine the measure of ∠q pls