A jar of 150 marbles costs $4.50. If the cost varies directly with the number of marbles in the jar, what should a jar of 250 marbles cost?

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!