Well the volume of dirt she needs to remove is equal to length*width*height=6.2*4.9*0.225=6.8355
Now let's find how many bags she needs.
To solve for this, simply divide room in bags from total room.
6.8355/0.87=7.857
Thus Zoe has barely enough, but enough bags.
#7 is the easiest one.
a + bi = -9 + 4i
see the expression on either side matches up so..
a = -9 and b = 4
To solve this problem you must apply the proccedure shown below:
1. You have the following points given in the problem above:

2. To find the midpoint, you must apply the formula that is used for calculate it. This is:

Where:

3. Now, you must substitute these values into the formula for calculate the midpoint, as following:

Therefore, the answer is: 