Geometry: Common Core (15th Edition)

$\frac{3}{7}$
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 are $3$ numbers that are not less than $10$, and 7 numbers in total. When we divide 3 by 7, we get $\frac{3}{7}$, which is the probability of choosing a number not less than ten, or $P(\nless 10)$