Answer
14.7 milligrams.
Work Step by Step
Let's assume the x is the milligrams of medicine to be given to patient weighs 210 pounds.
Now, we will write the proportion for the given details.
$\frac{3.5}{50} = \frac{x}{210}$
$3.5\times210 = x\times50$ (cross multiply)
$50 x = 735$
$x = 14.7 (divide by 50)
14.7 milligrams of medicine to be given to patient weighs 210 pounds.