2f+6+4f=6+6f
6f+6-6=6-6+6f
6f=6f
This means f can equal any number which we call mathematically infinite solution or infinitely many solutions
The answer to this problem is 5.
12 cm:102 ft
-------- ------
12 12
1 cm:8.5 ft
The scale is 1 cm equals 8.5 ft.