The answer is B) x is equal to all real numbers.
The domain of a function is the numbers for x that you can put in. Although the y-values are restricted here, you can put any number you want in for x. Therefore, x is equal to all real numbers.
Marked down 15% means the new price would be 85% of the original price ( 100%-15% - 85%)
Multiply the original price by 85%:
5250 x 0.85 = 4462.50
The new price is $4,462.50
The answer is it is yes, it is sometimes true, y can =0