Answers

2016-07-24T08:00:59+08:00
-{-[-2r-5s+3(r-2s)]-5(s-r)}
= -{-[-2r-5s+3r-6s]-5s+5r}
= -{-[r-11s]-5s+5r}
= -{-r+11s-5s+5r}
= -{4r+6s}
= -4r-6s

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