Jeans costs $15 each and shirts costs $9 each. you have at most $90 to spend clothing. you must purchase at least 3 pairs of jeans. let x be the amount of jeans purchased and y be the amount of shirts purchased. what is a possible solution?
(4,-5)
(4, 5)
(4,2)
(2,4)

If we check the possible outcome it is actually quite simple.

(4, -5)
We buy the required 3 pairs of jeans but you cannot buy negative amount of something so that is wrong

(4, 5)
We buy the required 3 pairs of jeans but the total price is 4*$15 = $60 + 5*$9 = $45 = $105 which is $15 too much

(2, 4)
We do not buy the required pairs of jeans, therefore this answer is incorrect as well

Finally we are left with (4, 2)
- We buy the required 3 pairs of jeans
- And the total price is $78, $12 less than the maximum amount of money we can spend

Bonus: If we wanted, we could buy another shirt and still be left with $3

The answer is 225 miles per 4.5 hours. hope this ; )