I'm really bad at math so I need some help explaining.

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

At the "no mutants allowed" country farm, every sheep has 4 legs, every chicken has two legs, and all animals have only 1 head. asked to count how many sheep and chicken are in the fields, a farm boy reports back that there are 140 feet and 50 heads. how many sheep and chicken are there? there are sheep and chicken at the farm.

100,000 random people were tested for condition a. roberto's doctor told him he tested positive for condition a. if the test is 99% accurate and condition a is rare—one out of every thousand people have it. what is the probability that testing positive means roberto has condition a? 99.0% 1% 9% 99.9%