Question 916586
Yes, 18C7 = 18!/ 7!(18-7)! ={{{(18*17*16*15*14*12)/(7*6*5*4*3*2*1)}}}=  31824 Using Calculator
...
IF the Order, the 7 choices, are in  matters...that's 18P7
18P7 = 18!/(18-7)! = 18!/11! =  {{{18*17*16*15*14*12}}}  = 160,392,960 (child's play on a calculator
These concepts has nothing to do with the order You multiply {{{18*17*16*15*14*12}}} = {{{18*16*17*12*14*15}}} for ex 
If You can use a calculator in class/testing... You must have one with a reasonable capability.
....
 Time is of an essence...in homework as well as testing.
Factorial capability (n!) is a minimum (and my guess would be any $12 calculator would have that n! button)
albeit it pricey, the TI83 or later is very popular for statistic students,
albeit it takes time to learn how to use it to its max.