Equivalence relation: sum of flowers (x) of 5 bouquets+remaining 4 flowers =39 flowers.

Column equation:

5X+4=39

5X=35

X=7

X=7 is the solution of the original equation.

The solution of the equation is X=7.

On average, seven flowers were used for each bouquet.

2. Solution: Suppose X people leave after graduation.

Reciprocal relationship: the sum of the number of male and female students-the number of people leaving after graduation (X)= the remaining 68 people.

Column equation:

(38+46)-X=68

84-X=68

X=84-68

X= 16

X= 16 is the solution of the original equation.

The solution of the equation is X= 16.

A: 16 people left after graduation.

(The above is by no means suspected of plagiarism, forgery, plagiarism or quotation. I hope it can be adopted. Thank you! )