representing trees within parentheses

I have found many examples on how to represent mathematical expressions as binary trees in parentheses but I cannot find how to translate a tree with just values, say integers, in parentheses format.

This is a mathematical expression example I was referring to. These examples are abundant, but how do you do this without operators?

y = m * x + b

( = y ( + ( * m x ) b ) )

(Sorry about all of the periods, I couldn't keep the spacing without them.)

.....=

/.......\

y........+

......./.....\

......*......b

..../...\

..m.....x

How would this expression look as a tree? Are there general rules on how to convert between the two representations?

( ( ( 3 7 ) 2 8 ) ( 9 7 ) 5 0 )