If Event A is “the card is a face card” and Event B is “the card is a spade,” demonstrate the equation holds true. / 52 = / 13 × / 52

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?

Pls! does anybody know a shortcut for answering these types of questions in the future?

If the wwight of a package is multiplied by 7/10 the result is 65.8 find the weight of the package