PLEASE HELP ME.

If private savings 'v' = 0.75s and total savings 's' equals $4.20 billion, solve for public and private savings.

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 $s$?

Mama mia restaurant used 1 2 2 1 ? of their mozzarella cheese making pizza and the remaining 6 4 64 ounces making pasta. how many pounds of mozzarella cheese did mama mia start with?