Mr. granville needs some plywood that is about three over four-inch thick. which plywood is closest to three over four-inch thick?

You need a set of choices to select.

I can convert the measure 3/4 inch to centimeters, so if the set of choices are in centimeters you can select the closest one.

1 inch = 2,54 cm

[3/4 inch]  * 2,54 cm/inch = 1,905 cm ≈ 1,90 cm

So, the answer is a number similar to 1,90 cm.