2)
If I understand your question, then:
5n mod 9 =<4
n =9a + 8, where a=1, 2, 3.........etc.
n=9*1 + 8..............1st pair.
n=9*22 + 8............22nd pair.
3)
The greatest such number is =928
928 - 1 =927 / 9 =103
928 -3 =925 / 5 =185
5. Compute 29^13-5^13 modulo 7.
29^13 - 5^13 =[2.4 x 10^14] mod 7 =2
8)
3 | 6 | 9 | 12 | 15 | 18 | 21 | 24 | 27 | 30 | 33 | 36 | 39 | 42 | 45 | 48
Add up all the units digits to get the sum.
9)
I cannot find an INTEGER solution for n
10)
2445 in base 6 = 605 in base 10, and:
605 / 11 =55
11)
x =2 and k =0.2
x =12 and k =0.04
0.2 + 0.04 =0.24