Formula for the area of a square = side^2
So, 15^2 will result in the area.
Thus, the answer is 225 mm^2 (when squaring, units are always given the square as well.)
To find points, we use the graphing technique or analytic algebra.
First, we need to find out how many houses that Hannah received money from. We can do this by dividing the total amount of money she received by the amount she received per house.
780 / 5 = 156
Hannah received money from 156 houses.
To find the amount of houses she did NOT collect money from, we just need to subtract the amount of houses that she DID receive money from away from the total amount of houses in her neighborhood.
278 - 156 = 122
Hannah did not collect money from 122 houses.
Hope this helped! =)