In a drawer there are only red pens, blue pens and purple pens. A pen is taken at random from the drawer. The table shows the probability of taking a red pen and a blue pen.
| Colour | Red | Blue | Purple |
|---|---|---|---|
| Probability | 112\displaystyle \frac{1}{12}121 | 712\displaystyle \frac{7}{12}127 |
Complete the table to show the probability of the pen being purple.