Your doctor informs you that you have been exposed to a virus that is contracted by 3 out of every 50 people exposed? Based on that information, what are the

Since you want the odds against you then you need to take the odds for you (3/50) and subtract them from a 1 to 1 odd (50/50).

You will get 47/50 or 94%

$3:50$

or

$\frac{3}{50}\times100$

$\frac{300}{50}$

6%

You have a $3$ in $50$ chance or 6% chance of contracting the virus.

Likewise

$50:50-3:50$

$47:50$

or

$\frac{50}{50}-\frac{3}{50}\times100$

$\frac{47}{50}\times100$

$\frac{4700}{50}$

94%

You have a $47$in $50$ chance or 94% chance of not contracting the virus.