Sally sold a decorated flowers that cost the same amount each plus a dozen roses for $28.all together she sold $73 in flowers. how much was each decorated flower?

To begin you must subtract the cost of the roses from the total cost of the flowers sold so $73-$28.  Then divide the remainder by the number of decorated flowers she sold to get the cost per each decorated flower.  I do not see in your question the number of decorated flowers she sold.  I see "a" so perhaps she sold one???