выполните умножение:
6/25*20/21=.
81/115*45/81=
5*2 1/5=
2 2/25*1 9/16=

6/25 * 20/21 = 120/525 =24/10581/115 * 45 / 81 =  3645 / 9315 = 9/235 * 2,1/5 =55/5 = 112,2/25 * 1,9/16 = 1300/400 = 13/4=3,1/4