Looking at the figure, we can see that both triangles are right triangles. Therefore, we can apply pythagorean theorems. A right triangle contains a hypotenuse, which is the longest side. In the figure, that would be sides with length 4 and 12. The equation for this is:
c = √(^2 + b^2) , where c is the hypotenuse and a and b are the other shorter sides
To determine z:
4 = √(z^2 + 3^2)
z = 2.65
To determine x:
12 = √(x^2 + 6^2)
x = 10.39