Germans paid 1.65 euros per liter of gasoline
American prices were $3.90 per gallon and for one liter = $3.90 / 4.55 = $0.86
One US dollar = 0.76 Euros
If Germans paid 1.65 euros for 1 liter, they will pay for 1 gallon = 1.65 euros x 4.55 liters = 7.51
Price of one gallon Germans paid in euros = 7.51 euros
As, 1 Us dollar=0.76 euros from this we get 1 euro = 1.31 dollars
So, price of one gallon Germans paid in dollars = 7.51 x 1.31 = $9.84
American gasoline have cost in euros per liter = 0.86 x 0.76 = 0.65 euros