How many solutions for a linear combination?

Calculate the missing value. round the answer to on decimal place. start with 70, increase it by 21%, and end up with

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 $s$?

The length of a field is 100 yards and its width is 75 yards. if 1 inch represents 25 yards, what would be the dimensions of the field drawn on a sheet of paper?