In a class of 30 students, 17 students study Chinese and r

3.In a class of 30 students, 17 students study Chinese and r students study Japanese. Every student studies either Chinese or Japaneseor both. How many students study both Chinese & Japanese?

(1) r=14

(2) 13 students take only Japanese

I pick D.

You know the following
Total students = 30
Students study Chinese = 17 (including ones enrolled in Japanese)
There are no students that study neither Jap or Chinese

1)
Total = Chinese + Japanese - Both
30 = 17 + 14 - Both ---> Both = 1 Sufficient

2)
Doesn't give you enough information. Doubt yourself.. see below
Let's say that Both = 0, then C+J = 17+13 = 30
Or Both can = 1, then C+J-Both = 17+14-1=30 (You add 13+1 to include the student who studies J and C to the total J count)
Answer two is insufficient