Zoo a has 109 monkeys while zoo b has 67 monkeys. which of the following is the best estimate of how many more monkeys zoo a has compared to zoo b.

So you mean like subtraction if so 109-67=42 .  Zoo A got 42 more monkeys than Zoo B

You would subtract 67 monkeys from 109 monkeys and you would get 42 more moneys and you would round to the nearest tenth so it would be 40 because five or greater add one more, and anything less it stays the same, all in front zero is your name.