(1)11.8x43-430x0.18=11.8*43-43*1.8=43*(11.8-1.8)=430.
(2).91+92+89+87+88+95+86+90+89+93
=90+1+90+2+90-1+90-3+90-2+90+5+90-4+90+90-1+90+3
=90*10=900