What is negative 13/7 minus negative 5/7 as a fraction

You are at a restaurant and owe $38 for your meal. you want to leave a 20% tip. how much will your tip be?

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Given a binomial distribution variable with n=20 and p=0.60 find the following possibilities using the binomial table a) p(x < 13) b) p x > 15) c) p(x = 17) d) p(11 < x < 14) e) p(11 < x < 14)