Find the law 1 / 2,4 / 5,9 / 13,16 / 25, (), ()

Find the law 1 / 2,4 / 5,9 / 13,16 / 25, (), ()

The upper molecules are 1 & sup2;, 2 & sup2;, 3 & sup2;, 4 & sup2;, the lower denominator is 2 = 1 & sup2; + 1,5 = 2 & sup2; + 1 & sup2;, 13 = 3 & sup2; + 2 & sup2;, 25 = 4 & sup2; + 3 & sup2;, so the fifth is 5 & sup2; / (5 & sup2; + 4 & sup2;) that is 25 / 41, and the sixth is 6 & sup2; / (6 & sup2;)

5.9.10.18.15.27_ ,_ Fill in the blanks according to the rules. What should I fill in the next two

5.9.10.18.15.27_ ,_.
It is divided into two columns
5,10,15,20,...
9,18,27,36, ...

8. 17, 5, 10, 11, 9, 12, (), 18 fill in the blanks according to the rules

It is a positive solution

3,6,18; 9,47,25; 6,31,17; 4, (), 15; 5, (), (). How to find the law?
What are the numbers in brackets?

3*1+3=6 3*7-3=18 1+7=8
9*5+2=47 9*3-2=25 5+3=8
6*5+1=31 6*3-1=17 5+3=8
4*4+1=17 4*4-1=15 4+4=8
5*4+1=21 5*4-1=19 4+4=8