The image shows a right triangle with hypotenuse labeled M. The sides are given as 3 and 4. This is a classic 3-4-5 right triangle. Therefore, the hypotenuse M is 5, found using the Pythagorean theorem:

$M^2=3^2+4^2=9+16=25$

$M=\sqrt{25}=5$

Final Answer: 5