CPhill

At 45 degrees and every ± 180 degrees after that

C(6,2) =  15 different combos

LOL!!!...don't shoot the messenger just because the message is unpleasant....!!!

Cool graphics, Mel  ....this visual really helps to see what is going on...!!!

Let N be the number of minutes when the planes are at the same altitude..so we have

520 +40N = 3800 - 120N      add 120N to both sides.....subtract 520 from both sides

160N = 3280                        divide both sides by 160

N = 20.5 minutes

-3(2k-6)=12     divide both sides by -3

2k - 6 = -4        add 6 to both sides

2k = 2               divide both sides by 2

k = 1

Yep.....

On your second trip, you pay $37.50 for two more pairs of sweatpants...so...they must be $18.75 each

And (85.50 - 37.50) / 3  gives the price of each sweatshirt = $16

The answer is "undefined"

To see why....note that

0 / 0 = a      but what's "a" ???     ...it could be anything ...because multiplying "a" by the denominator of 0, we get the numerator 0......but since 0 times anything = 0, then "a" could be anything.....thus it's undefined...!!!