The Pythagorean theorem is: a²+b²=c², and "c" will always be the hypotenuse or the longest side of the triangle.
In order to find MN you can make a triangle, and then you can find the lengths of the other sides(a and b).
You should get a = 4 and b = 6. Next you plug these numbers into the equation.
(4)² + (6)² = c²
16 + 36 = c²
52 = c²
√52 = c
