Thirty percent of the members of a swim club have passed the lifesaving test. Among the members who have not passed the test, 12 have taken the preparatory course and 30 have not taken the course. How many members are there in the swim club?
30% of the members have passed the test, thus 70% have not passed the test.
We also know that 30+12=42 members have not passed the test, thus 0.7*Total=42 --> Total=60.
The approach provided above can be used to solve this problem easily. however, i want to point out that this could also solved by using double sided set matrix method, similar to the problem which Bunuel explained at