In a raffle, scott buys 10 tickets and his friend tom buys 6 tickets. if there are 80 tickets sold, what is the probability that scott or tom will win?

80 tickets in total. 
-scott has 10 
-tom has 6 

you've gotta make those into fractions (a fraction is part of a whole number) 
let's do scott first, 
the total amount of tickets is 80, right? 
Scott bought 10 out of the 80 
the fraction will look like this 10/80 (to the lowest terms it's 1/8) 
put that into your calculator as (1/8) x 100 and it will give you the probability %

you do the same for tom: 
he bought 6 out of 80 tickets 
the fraction will be 6/80 (lowest terms = 3/40) 
put that into your calculator as (3/4)x 100 and you got your probability %