So for this you're gonna be using proportions to solve.
[tex] \frac{1}{398} = \frac{x}{90000} [/tex]
Cross multiply to get [tex]398x=90000[/tex]
Then just divide by 398 on each side, and you'll get x ≈ 226
In short, you'll need to make approximately 226 pizzas to be able to make $90,000.