The following table demonstrates the relation between interest rate, principal investment, and amount of interest. Fill in the missing entries with expressions or numbers.

Organize data with a table
Rate $\times$Principal$=$Interest
Solution 1$36$% $100$ $36$
Solution 2$28$% $900$
Solution 3$50$% $26$
Solution 4$7$% $320$
Solution 5$6.4$% $420$
Solution 6$8$% $x$
Solution 7$6.2$% $3000-x$