We have,
No. of good pens = 132
No. of defective pens = 12
So, the total no. of pens = 132 + 12 = 144
Then, the total no. of possible outcomes = 144
Now, let E = event of getting a good pen.
No. of favourable out comes = 132 {132 good pens}
Probability, P(E) = Number of favourable outcomes/ Total number of outcomes
P(E) = 132/144 = 11/12