Step One
Find AM
Formula
AM = MN - AN
Givens
MN = 67.2
AN = 32
Solution
AM - 67,2 - 32
AM = 35.2
Step Two
Set up a solution
67.2/35.2 = 81.9/x Cross Muliply
67.2 * x = 81.9 * 35.2 Combine the right
67.2 * x = 2882.88 Divide by 67.2
x = 2882.88/67.2
x = 42.9 Answer