The reason this problem is so sneaky is that it has a lot of
different units in it, and you have to keep them all straight.
Volume of concrete for the patio = (length) x (width) x (height).
You know all of these dimensions, but be careful. Before
you multiply them, they must all be in the same units.
Length = 36 ft
Width = 24 ft
Height = 9 inches = 3/4 of a ft (0.75 ft).
NOW you can multiply to get the volume.
Volume = (36 ft) x (24 ft) x (0.75 ft) .
The result is the volume in ft³ (cubic feet).
Now you need to figure out how much this will cost, but you run into
another problem . . . you know how much each yd³ costs, but you
only have the volume in ft³. You have to change the ft³ into yd³ .
Here's the tool you need to do that: 1 yd³ = 27 ft³
The rest is just arithmetic. I know you can handle it from this point.