1) 2,16÷2.7/10+0,3·1.4/5 = 216/100 * 10/27 + 3/10 *9/5 = 4/5 + 27/50 = (40+27)/50 = 67/50 = 1.17/50
2)1.3/4÷25+0,4·1,9= 7/3*1/25 + 76/100 = 7/75 + 76/100 = (70+5700)/7500 = 5770/7500=577/750
3)6,25·1/5+0,64 = 25/4 *1/5 +0,64 =5/4 +0,64 = 1,25+0,64=1,89