5 1/13 * 0,65 = 66/13 * 65/100 = (33*5)/(1*50) = 165/50 = 330/100 = 3,3
9/16 * 1/3 = (3*1)/(16*1) = 3/16
72 * 5/6 = 12 * 5 = 60
5/7 * 0,42 = 5/7 * 42/100 = (1*6)/(1*20) = 6/20 = 3/10 = 0,3
4 1/5 * 7/10 = 21/5 * 7/10 = 147/50 = 294/100 = 2,94
