Bài 1:
\(a,-248+403+\left(-155\right)=155-155=0\)
\(b,-16+128-89+877=112-89+877=23+877=900\)
\(c,-17-260+\left(-25\right)+260=-17-260-25+260=\left(-260+260\right)+\left(-17-25\right)=0+\left(-42\right)=-42\)\(d,-15-124-\left(-134\right)-14=-139+134-14=-5-14=-19\)
\(e,133+134+134+136-33-34-35-36\)
\(=\left(133-33\right)+\left(134-34\right)+\left(135-35\right)+\left(136-36\right)\)
\(=100+100+100+100\)
\(=4\times100\)
\(=400\)
Bài 3:
\(a,264+\left(2x-125\right)=237\)
\(2x-125=237-264\)
\(2x-125=-27\)
\(2x=-27+125\)
\(2x=98\)
\(x=98:2\)
\(x=49\)
Vậy ...
\(b,63-\left(-59+x\right)=277\)
\(-59+x=63-277\)
\(-59+x=-214\)
\(x=-214+59\)
\(x=-155\)
Vậy ...
\(c,-\left(2x+44\right)+311=-133\)
\(-2x-44=-133-311\)
\(-2x-44=-444\)
\(-2x=-444+44\)
\(-2x=-400\)
\(x=-400:\left(-2\right)\)
\(x=200\)
Vậy ...
\(d,725-\left(725-x\right)=-43-126\)
\(725-\left(725-x\right)=-169\)
\(725-x=725+169\)
\(725-x=894\)
\(x=725-894\)
\(x=-169\)
Vậy ...
\(e,-46-\left(-x-513\right)+\left(-254\right)=667\)
\(-46-\left(-x-513\right)=667+254\)
\(-46-\left(-x-513\right)=921\)
\(-x-513=-46-921\)
\(-x-513=-967\)
\(-x=-967+513\)
\(-x=-454\)
\(x=454\)
Vậy ...
