First you need to get rid of the parenthesis by distributing the 0.6 to each term inside.
(0.6)(10n) + (0.6)(25) =10+5n
6n +15 = 10+5n subtract the 5n on both sides and subtract 15 from both sides
6n-5n = 10-15
n=-5
Option B : The area of the circular base multiplied by the height of the cylinder
5 odd numbers and 5 even numbers
since they can be repeated
5*5*5=first 3 digits
5*5*5=last 3 digits
in all
5*5*5*5*5*5=15625 ways
The base is 5 because the base = 2 Area/Height