What is the cost of 1 dozen carnations if 30 cost $50.00?

Let's create a ratio of amount to price

if

30:$50

then

12:x

30/12 = 2.5

50/2.5 = 20

30:$50

12:$20

Another way of looking at it is like this:

If 30, costs $50, then each 3 would cost $5. Four groups of 3 in 12. 4 * $5 = $20

30/$50=12 (the dozen) / x. x is the cost of a dozen carnations. Cross multiply for 30x=600. Divide both sides by 30 to get x by itself. x=20. $20 per dozen.