Find the current exchange rate between the U.S. dollar (USD) and the Mexican peso (MXN). You can find the current exchange rate on websites like Exchange-Rates.org or X-Rates.com. Alternatively, search Google for "peso dollar exchange rate". Google will display a Google Finance widget with the current exchange rate between the two currencies above the results of your web search.
Multiply the number of pesos you have by the exchange rate, which will be in dollars-per-peso. For example if you have 100 MXN and the exchange rate is .08 dollars-per-peso, multiple 100 by .08 to get 8, or $8 USD. As long as the exchange rate is less than one, the peso will be worth less than the dollar.
Check your work by dividing the number of dollars you got in Step 2 by the exchange rate you found in Step 1. Continuing with the previous example, you'll need to check that 100 MXN converts to $8 USD when the exchange rate is .08 dollars-per-peso. Divide 8 by .08 using a calculator. Since the result is 100, you know your initial conversion was correct.
Check your work by using a free online currency converter like the one available on Yahoo! Finance if you don't have a calculator. Enter "MXN" in the first field and enter the number of pesos you'd like to convert. Enter "USD" in the second field. The page will update and the answer will appear.
