help please

i need help on my geo hw.... i need to find sin for R and S when RT=20,TS=15 and SR=25 and no angles are given eccept that it is a right triangle and angle T is 90. so i got that sin S = opp. angle S over hypo.=rt over sr = 20 over 25... now idk how im supposed to find sin S with a the fraction 20 over 25. please make a video or explain what i have to punch in the calculator. thanks


















