Bags X and Y each contain counters. Bag X
30 counters
Each counter is green, white or yellow
Bag Y
5 counters
3 green and 2 red

P(green counter from X) = P(red counter from Y)
Work out the number of green counters in X.

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 expression is equivalent to log3(x+4)

Witch sequence shows a pattern where each term is 1.5 times the previous term