Chapter 6 - Section 6.4 - Permutations and Combinations - Exercises - Page 438: 64b

$27$

3 tech stocks increased in value by the end of the day. We can choose two out of these in $C(3,2)=3$ different ways. We can choose the third stock out of the other 9 stocks. We can do that in $C(9,1)=9$ different ways. This gives a total of $3*9=27$ such collections.