This is a DLO on how to use a protractor. You will need to figure out where the center of the protractor is, next figure out where the lines go and then measure from the zero. When you measure the number / line that could be the nearest. If the line is in the middle of the two numbers you look at which side is the biggest number and then go down to the lower number.
example 40 39 38 37 36 35 34 33 32 31 40 the biggest number is 30 so you go down to 30 and so then the answer is 35.