math
posted by jessica .
A certain medicine is given in an amount proportional to a patient’s body weight. Suppose that a patient weighing 100 pounds requires 125 milligrams of medicine. What is the weight of a patient who requires 200 milligrams of this medicine?
I am totally lost on how to work this problem. Someone please help!

Use a proportion, cross multiply, and solve for x.
100/125 = x/200