Question 1004864
Hi there,
I assume that the sandbox is being  placed
on the lawn and you want to know how much lawn
is left.
Area of lawn = 79 1/3 x 72 = 5712 ft^2
Area of sandbox = (3.5)^2 = 12.25 ft^2
5712 - 12.25 = 5699.75 ft^2 of lawn left.
Hope this helps :-)