One way to multiply a whole number bay fraction.

turn the whole number to a fraction by simply writing 1 underneath it. Example, 9 --> 9/1

Any fraction over one is the number itself like how 9/1 = 9

So then you can do like

9 x 2/3 --> 9/1 x 2/3 = 18/3

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225