脱式计算5-5/14÷3/4+22/776.3×5/9+27-4/513/50÷8/15÷34/406.2÷9/56.2÷9/6+2.5×5/9化成最简整数比2.4:0.752.5:3/48/9:14/15口算8/15-4/5