You can substitute the blank for the variable x. So the equation is now 40,000÷x = 400. Now you must multiply both sides by x to get that 40,000=400x. Next, in order to isolate the variable you divide both sides by 400 to get that x=100.
$120 because the fencing of the patio would use up eight squares and each square in the picture is 3 meters so we would need 24 meters of fencing to cover up the entire patio. Since it cost $5 for one meter, 5*24 is $120.
