a) `(-2436+1327)-(2436+327)`
`=-2436+1327-2436-327`
`= -2436 xx 2 + (1327-327)`
`=-4872 + 1000`
`=-3872`
b) `-(134+24-35)-(135-124-66)`
`=-134-24+35-135+124+66`
`=(124-134-24)+(35-135)+66`
`=-34 - 100+66`
`=-68`
c) `-209+436-91+64`
`=(-209-91)+(436+64)`
`=-300 + 500`
`=200`