Which algebraic expression is a polynomial? a.) -6x³ + x² - √5 2 b.) 4x² -3x + x c.) 8x² + √x?

The correct answer is b.  
A polynomial is an expression that contains terms with the form ax^n where a is equal to any number (negative or positive) and n is the power, or exponent, of x (squared, cubed, etc.). In order for it to be a polynomial, the exponent must be positive. Terms that contain square roots are not polynomials as the exponent is considered radical (1/2). Thus, b is the correct answer.

There are several information's already given in the question. Based on those information's the answer can be easily deduced.
The equation given in the question is 
T = 10x + 1000
When the ticket rate is increased to $15, the equation becaomes
T = 15x + 1000
4000 = 15x + 1000
15x = 3000
x = 200 tickets
From the above deduction, it can be concluded that the correct option among all the options that are given in the question is the third option or option "C".