If a given variable varies directly with another variable, it means that an increase in the value of the given variable results in a corresponding increase in the value of the other variable. Also, a decrease in the value of the given variable results in a corresponding decrease in the value of the other variable.
If value of y varies directly with x, we would introduce a constant of variation so that the expression becomes
y = kx
When x = 13, y = 104. Substituting into the above expression, it becomes
$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.
