Answer:
45
Step-by-step explanation:
As a first rough estimate: divide 390 by 10, obtaining 39.
Another reasonable approximation could be obtained by dividing 450 by 9 and 360 by 9, obtaining 50 and 40. Since 390 is roughly halfway between 360 and 450, estimate that the quotient is approx 45 (halfway between 40 and 50).
