クレジットカードはつかえますか？ Can I use a credit card? /Am I able to use a credit card? This is probably the best sentence in this situation --- は使えますか？Can I use-----? Can I use cash? げんきんはつかえますか？

クレヂトカードはつかってもいいですか クレヂトカード = credit card つかって = is a versatile verb form used to ask for something / permission to do something. In this case, "to use" もいいですか = is the ending used when asking "[am i] allowed to [?]"