understanding probability

Question

A bag of balloons contains 3 red balloons, 10 green balloons, 15 yellow balloons, and 7 orange balloons. What is the probability that a randomly selected balloon would be green or orange?

 A. 

 B. 

 C. 

 D. 

Answer 1

The answer is:

(the number of green balloons + the number of orange balloons)

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(the total number of balloons)

There are 3+10+15+7 balloons in total. There are 10+7 balloons that are either green or orange.