Conversion questions come down to one decision: multiply or divide? Write the rate with its units and the units will tell you.
If 1 USD = 0.92 EUR, then 250 USD = 250 × 0.92 = 230 EUR, and 230 EUR = 230 ÷ 0.92 = 250 USD. To go from euros to pounds when the table only gives rates against the dollar, go through the dollar: euros to dollars, then dollars to pounds.
Use the rate the test gives you, even if you know a more exact one, and read any rounding rules in the notes. Converting to a smaller unit gives a bigger number.
A ratio of 3:5 splits a total into 8 parts: find one part first, then scale it. Rates work the same way. Cost per unit × units = total, and total ÷ units = cost per unit.
One sense check catches most slips: converting into a currency that's worth less per unit should leave you with more units, not fewer.