The task is to generate the correct answer for a given math problem.

Problem: a student chose a number , multiplied it by 2 , then subtracted 138 from the result and got 102 . what was the number he chose ?
120

Problem: in a garment industry , 12 men working 9 hours per day complete a piece of work in 10 days . to complete the same work in 12 days , working 15 hours a day , the number of men required is :
7

Problem: by selling an article for $ 195 , a person gains $ 45 . what is the gain % ?
30 %