You did not include the questions, but I will give you two questions related with this same statement, and so you will learn how to work with it.
Also, you made a little (but important) typo.
The right equation for the annual income is: I = - 425x^2 + 45500 - 650000
1) Determine the youngest age for which the average income of a lawyer is $450,000
=> I = 450,000 = - 425x^2 + 45,500x - 650,000
=> 425x^2 - 45,000x + 650,000 + 450,000 = 0
=> 425x^2 - 45,000x + 1,100,000 = 0
You can use the quatratic equation to solve that equation:
x = [ 45,000 +/- √ { (45,000)^2 - 4(425)(1,100,000)} ] / (2*425)
x = 38.29 and x = 67.59
So, the youngest age is 38.29 years
2) Other question is what is the maximum average annual income a layer can earn.
That means you have to find the maximum for the function - 425x^2 + 45500x - 650000
As you are in college you can use derivatives to find maxima or minima.
+> - 425*2 x + 45500 = 0
=> x = 45500 / 900 = 50.55
=> I = - 425 (50.55)^2 + 45500(50.55) - 650000 = 564,021. <--- maximum average annual income