Euros per dollar:
35 / 45 = 0.78
Dollars per euro
45 / 35 = 1.29
*** The answer is b. 0.78 ***
The question is asking the exchange rate in euros per dollar. To find this we divide the 35 received euros by the 45 usd given to get 0.78. For every €0.78 , it is equivalent to 1 usd.
The reverse of this is usd per euros, so for every $1.29 it is equivalent to 1 euro.
I hope this helped