The question mentions the keyword, "temperature drops" meaning we need to alternatively subtract.
If we know that positive 2 times 12 is 24, we know -2 times 12 will be negative 24°, because any negative number times a positive number is <em>always </em>a negative number.
Ok, so the most she can carry is 4 books. and they weigh 1 - 3.5 lbs. so you take 1 times 4. and thats well 4. then you do 3.5 times 4. thats 14 so your range would be 4 -14 lbs
