If Currency R strengthens relative to Currency S, will the exchange rate in terms of units of

Question:

If Currency R strengthens relative to Currency S, will the in terms of units of S per unit of R increase or decrease? Explain.
Exchange Rate
The value of one currency for the purpose of conversion to another. Exchange Rate means on any day, for purposes of determining the Dollar Equivalent of any currency other than Dollars, the rate at which such currency may be exchanged into Dollars...