(324又7分之1-810又6分之1+486.5)x4.2 简便运算 急~~~~~~~~~~~~~~~~~~~~~~~~

(324又7分之1-810又6分之1+486.5)x4.2
=(324+486-810+1/7-1/6+1/2)x4.2
=（1/7-1/6+1/2）x4.2
=1/7x4.2-1/6x4.2+1/2x4.2
=0.6-0.7+2.4
=2.3

是2，我有教材的（324又七分之一减810又六分之一+486.5）乘4.2
=(324-810+486+1/7-1/6+0.5)x4.2
=(1/7-1/6+0.5)x4.2
=0.6-0.7+2.1
=2