It would cost 49.96 to order three Cd's.
14.99*3=44.97
44.97+4.99=19.96.
Hope this helps
4x+30=90
4x = 60
x = 15
answer is B. 15
We must find UNIQUE combinations because choosing a,b,c,d... is the same as d,c,b,a...etc. For this type of problem you use the "n choose k" formula...
n!/(k!(n-k)!), n=total number of choices available, k=number of choices made..
In this case:
20!/(10!(20-10)!)
20!/(10!*10!)
184756
Well one dm= 10 cm
12-10= 2 cm