PLEASE HELP I NEED IT: You have a triangle with one 70 degree angle and one 40 degree angle. What is the measure of the other angle?

As a manufacturer of golf equipment, the spalding corporation wants to estimate the proportion of golfers who are left-handed. how many golfers must be surveyed if we want 99% confidence that the sample proportion has a margin of error of 0.025? assume that a previous study suggests that 20% of golfers are left-handed.