55乘98加110 =55x98+55x2 =55x(98+2) =55x100 =5500 550+55乘68+22乘55 =55x10+55x68+22x55 =55x(10+68+22) =55x100 =5500 4000除以160 =4000÷40÷4 =100÷4 =25