what does the below rebus means?

Replace the question mark with the number below given a simple math problem.

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

Solve the following series:
AZ, GT, MN, __, YB

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

Can you make a six-letter word using the letters N, A and B ?

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?

Can you replace the question mark with the correct number in the below table sequence?