ex1
A=-3.5+2.4-14.5+1+2.6
=-3.5-14.5+2.4+1+2.6
=-18+6
=-12
B=-2.7+0.3-5.3+1.7-2
=-2.7-5.3-2+0.3+1.7
=-10+2
=-8
ex2
A=2.5×(-0.6)×(-4)
=2.5×2.4
=6
