Find value of z. give the answer in simplest radical form

Assuming Z is the length of the third line, you'd count the squares between each point to get the lengths, (3 at the top, 5 along the side), and then use Pythagoras' theorem. So, 3 squared + 5 squared = Z squared. 9 + 25 = 34, so your answer in radical form is √34. I hope this helps!