Find the molar mass of both of them so Cu is 63.5g/mol and Ag is 107.8g/mol and then divide the mass in grams for each by the molar mass of each to get the number of moles so 56g/107.8g=.52moles and 22g/63.5g=.35moles. Add the number of moles together and divide the number of moles of silver by that sum so .52mol+.35mol/.35=2.4*100%.