Сократите дробь 20/45; 12/72; 136/170,21/108; 24/36; 15/35/102/136; 90/126; 3/39; 36/63/21/84; 151/302; 130/182; 490/560; 10/75. !

20/45=4/912/72=1/3136/170=4/521/108=7/3624/36=2/315/35/102/136=3/7/51/68=3*68/7*51=68/7*17=68/119=4/790/126=5/73/39=1/1336/63/21/84=4/7/1/4=4/7*4/1=2  2/7151/302=1/2130/182= 5/7490/560=7/810/75= 2/15