Why do some letters like C and D are mot parallel, perpendicular, or intersect

Which of the following represents a number squared is equal to twenty more than nine times that number ? a) x squared = 9x + 20 b) x squared = 20x + 9 c) x squared > 9 + 20x d) x squared = 9 + x + 20

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

If it 8 inch candle burns at 7/10 inch per hour and a 6 inch candle burns at 1/5 inch per hour after how many hours would both candles be the same height