9*31'-2*58" 4*17'19''-3*39'58'' 1*-1'' 1*-59'59''+1''
9*31'-2*58"=9*30'60"-1*60'58"=8*90'60"-1*60'58"=7*30'02" 4*17'19''-3*39'58''=4*16'79''-3*39'58''=3*76'79''-3*39'58''=37'21'' 1*-1''= 60'-1"=59'60"-1"= 59'59" 1*-59'59''+1'' =0