Three times the variable m minus four is equal to fourteen.
Another way could be:
Four less than three multiplied by m is equivalent to fourteen.
The first way I put it is simpler but if you really want to impress your teacher then I suggest going with the second way.
Also if you are looking to solve the equation then it would be:
3m - 4 = 14
+4 +4
------------
3m = 18
----- -----
3 3
m = 5
Hope that helped :-)