Geometry: Common Core (15th Edition)

$\frac{10}{11}$
To calculate probability, we need to divide the number of chances for a certain outcome to occur by the total number of outcomes. In this case, there is $1$ tile with the letter "M", and $11$ tiles in total. This means that the other $11-1=10$ tiles must be "not M". When we divide $10$ by $11$, we get $\frac{10}{11}$, which is the probability of drawing a letter that is not "M", or $P(\text{Not M})$