That would be 4(16) - 8 - (4(0) - 8) = 64 - 9 - 0 + 8 = 63 Answer
Each book costs $34 for this problem you need to first subtract 18 from 324 which gets you 306 then divide 306 by 9 and you get 34
You need to work out the area so
Area of a rectangle is l x b
So
A= l x b
A= 8 x 4
A= 32
Therefor 32 cubic feet of dirt is needed
For the first digit there are 7 choices. For the second digit there are 6 choices (because we can't use the same one again). And so on, until there is only one choice for the last digit.
The number of possible codes is this:
7*6*5*4*3*2*1 = 7! = 5040
