Use the following steps to calculate this result:
Step 1: Put the quote in direct terms. (Remember: The bid will become the ask and the ask will become the bid).
Bid: 1.00000 / 8.50000peso/$ = 0.11765$/peso
Ask: 1.00000 / 8.00000peso/$ = 0.12500$/peso
Step 2: Calculate how many pesos can be purchased for $100.00
Since we are buying pesos, we have to buy at the ask price of 0.12500$/peso. 100.00000$ / 0.12500$/peso = 800pesos.
Alternate method:
For the examination, remember that the bank must make its profit through the bid-ask spread (the foreign-exchange market is typically transaction-fee free), so you will always buy at the "high" price and sell at the "low price." Here, the "high" price is 8.00000peso/$ (At 8.00000peso/$ the peso is worth more than at 8.50000peso/$).
100.00000$ × 8.00000peso/$ = 800.00000peso