Heaven has 40% off of 350 dollars but she has to owe 40 dollars more. how much money is left of 350?

Find the area of the regular hexagon if a side is 20 cm.

Out of $20$ creepy-crawly creatures in a room, $80\%$ are flies and $20\%$ are spiders. if $s\%$ of the total legs belong to spiders, what is $s$?

Whats are the trickiest steps to do when adding or subtracting rational expressions? how does knowledge of rational numbers u in adding and subtracting rational expressions?