Dan bought a new house with a backyard whose dimensions are 21.8 by 12 feet. the backyard has a triangular garden with an area of 34.56 square feet. dan wants to cover the backyard with seeds so that the grass will grow. if he does not need to cover the garden, how many bags of seed must he purchase to cover the rest of the backyard if one bag covers 16 square feet?

Well first, let's find the total area of the back yard.  Given the dimensions, we can assume the yard is rectangular.
Area = 21.8(12) = 261.6ft²

Now we can find the area that will need to be seeded by subtracting the area of the garden from the total area:
261.6 - 34.56 = 227.04ft²

Finally, we can divide this area by 16ft² to find the number of bags of seed we will need.  
227.04 ÷ 16 = 14.19 bags  or little more than 14 bags.. Looks like we better buy 15 bags of grass seed to do the job..