раскрыть скобки и упростить -4*(1.3a-2)-(-5a+8)
0.4:(10m-5n)-2*(3m-n)
-1/3*(3a+9b)+1/5*(5a-10b)

-4*(1.3a-2)-(-5a+8)=-5,2a+8+5a-8=-0,2a

0.4*(10m-5n)-2*(3m-n)=4m-2n-6m+2n=-2m

-1/3*(3a+9b)+1/5*(5a-10b)=-a+3b+a-2b=b
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