Aratio of equivalent values used to express the same quantity in different units

Carl wants to buy a television that cost $500 including taxes. to pay for television he will use a payment plan that requires him to make a down payment of $125 and then pay $70.50 each month for six months what is the percent increase from the original cast of the television to the cost of the television using a payment plan.

What's the difference between: x≥0 and nonnegative integer. ?

What term makes it inconsistent y=2x - 4 ?