The expression is 66 of 90.

The percent is 0.66 and the whole is 90. You need to find the part.

Let n represent the part.

Part = percentwhole

n = 0.6690                   (Substitute percent = 0.66 and whole = 90)

n = 59.4                          (Multiply: )

59.4 is 66 of 90.