Another 3rd grade question:
the rec center soccer field measures 35 yards by 65 yards. chris dribbles the ball around the perimeter of the field 4 times what is the the total amount of yards that chris dribbles the ball?

To find the perimeter you would need to add 35+35+65+65=200. If the perimeter is 200, and he circles around it 4 times, 200*4=800, which is the answer. 
  The total amount of yards that Chris dribbles the ball is 800 yards.

1. isolate the variable, in this case, d. subtract 35.5 on both sides of the equation.2. 52 subtracted by 35.5 is 16.53. therefore your answer would be d= 16.5this is the basics of pre algebra, isolating variable through adding, subtracting, multiplying, and dividing, if you have any other questions to ask just comment!