[tex]6\frac{1}{2}[/tex], "six and one over two ft".
Let's considerate the fact that the garden has a square shape.
Amount of fence that the gardener already has: [tex]4\frac{1}{2}[/tex] ft.
Length of one side: [tex]2\frac{3}{4}[/tex] ft.
If one side measures [tex]2\frac{3}{4}[/tex] ft, and the square garden has 4 sides of equal length, because it's a square, then we must multiply the measure of one side by 4 to find the total length of fence needed:
[tex]4*(2\frac{3}{4})=\\ \\4*(2+\frac{3}{4})=\\ \\(4*2)+(4*\frac{3}{4})=\\ \\8+(\frac{12}{4} )=\\ \\8+3=\\ \\11[/tex]
The gardener already has [tex]4\frac{1}{2}[/tex] , which equals [tex]4 + \frac{1}{2}[/tex]. Hence, the difference between the amount needed and the amount that the gardeneralready has will give us the remaining amount required. Let's do that:
[tex]11-(4+\frac{1}{2} )=\\ \\11-(\frac{8}{2} +\frac{1}{2} )=\\ \\11-\frac{9}{2}= \\ \\\frac{22}{2} -\frac{9}{2}=\\\\ \frac{13}{2}[/tex]
[tex]\frac{13}{2} =\\ \\\frac{2}{2} +\frac{2}{2} +\frac{2}{2} +\frac{2}{2} +\frac{2}{2} +\frac{2}{2} +\frac{1}{2}= \\ \\6+\frac{1}{2}=\\ \\6\frac{1}{2}[/tex]