Answer: to make 78 copies it cost 26 dollars.
Step-by-step explanation:
18 copies - 6 dollars
78 copies - x dollars
Hence,

If you are charging 5 per hour use h to determine how many hours and add 10 for the connection fee
5h+10
Step-by-step explanation:
if you're looking for x
x=180-42-51= 87°
and if you're looking for D
D= 180-42= 138°
Answer is 676,000 possible passwords
xxx##
There are 10 possibilities for each digit placed and 26 possibilities for each letter placed.
10x10x10x26x26 = 676,000