It is already given in the question that the area of Danielle's garden is 1/2th of her entire or total yard. So the garden takes a partial part of the total yard is understandable from the question.
Let us assume the area of Danielle's yard = x
Area of Danielle's garden = 10 square feet
Then we can write the equation as
(1/12)x = 10 square feet
x/12 = 10 square feet
x = (10 * 12) square feet
= 120 square feet
So the area of Danielle's total yard is 120 square feet. This is the easiest process of getting to the answer for this type of problems. Hope you have understood the method and can solve such problems on your own in future.