1:<br/>I gotta hand it to you. You certainly made this party a success.<br/>I gotta hand it to you. You've certainly made this party a success.<br/><br/>2:<br/>See, you can do it if you try.<br/>See, you can do it if you tried.<br/><br/>Please tell me which of them are grammatically correct.<br/><br/>Also,<br/><br/>I knew you could do it if you tried.<br/><br/>Is this sentence correct?<br/><br/>Thank you.