[- 2] x [ - 7 ] x [ - 5 ] x [ - 七分之一 ]
=10×1
=10
[0.25] x [ -九分之七 ]x 4x[-18]
=（0.25×4）×【（-7/9）×（-18）】
=1×14=14
[-3]x[+56]x[-145]x0x[+127]
=0