On a trip, you had to change your money from dollars to euros. you got 450 euros for 600 dollars. which is a unit rate that describes the exchange? a.0.75 euros per dollar b.4.5 euros per dollar c.6 euros per dollar or d.6 euros per dollar

The number of Euros received against 600 dollars = 450
Then
For 1 dollar, the number of euros = (450/600) euros
                                                       = (45/60) euros
                                                       = ( 3/4) euros
                                                       = 0.75 euros
So the unit rate that describes the exchange rate is 0.75 euros per dollar. So the correct option among all the options given in the question is option "A". I hope the procedure for getting to the correct result is clear enough for you to understand. In future you can use this procedure for solving similar problems.