Solve for y in the two equations below using substitution 4x - 16y=20 4x+16y=180 a. y=25/4 b. y=10 c. y=25 d. y=5

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?

Reflect the point (7,0) across the y-axis

Leslie started last week with $1200 in her checking account. during the week, she wrote the checks below.