Simplify just started math class and it’s super hard : )

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?

Can u guys do this ratio question. this is extremely urgent a tap is leaking water at a rage of 1l every 8 hours. how long will it take for the tap to leak a total of 300ml?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.