There are 10 millimeters in one centimeter (centi means 10). 500 millimeters to centimeters (divide by ten) would be 50 centimeters. 50 centimeters added to 30 centimeters is 80 centimeters total.
You would use the slope formula which is (y2-y1)/(x2-x1) where x1 and y1 correspond to the first point and x2 and y2 correspond to the second point. This would be (5-2)/(9-6) which equals 1. Hope this helps!
