How many litres of pure antifreeze should be added to 5 litres of 30% antifreeze solution to create a 65% antifreeze solution?

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 serenity and the mystic are sail boats. the serenity and the mystic start at the same point and travel away from each other in opposite directions. the serenity travels at 16 mph and the mystic travels at 19 mph. how far apart will they be in 3 hours?

∠a and ∠ b are complementary. if m∠ b = 80°, what is the measure of ∠ a? 10° 80° 90° 100°