Bài 1:
a) \(215+\left(-38\right)-\left(-58\right)+90-85\)
\(=215-38+58+90-85\)
\(=\left(215-85\right)+\left(-38+58\right)+90\)
\(=130+20+90\)
\(=240\)
b) \(917-\left(417-65\right)\)
\(=917-417+75\)
\(=500+75\)
\(=575\)
c) \(31-\left[26-\left(2017+35\right)\right]\)
\(=31-\left(26-2017-35\right)\)
\(=31-26+2017+35\)
\(=\left(31+35-26\right)+2017\)
\(=40+2017\)
\(=2057\)
d) \(54+\left(-37+10-54+67\right)\)
\(=54-27+10-54+67\)
\(=\left(54-54\right)+\left(-27+67\right)+10\)
\(=0+40+10\)
\(=50\)
e) \(\left(326-43\right)+\left(174-57\right)\)
\(=326-43+174-57\)
\(=\left(326+174\right)-\left(43+57\right)\)
\(=500-100\)
\(=400\)
f) \(\left(351-875\right)-\left(125-149\right)\)
\(=351-875-125+149\)
\(=\left(351+149\right)-\left(875+125\right)\)
\(=500-1000\)
\(=-500\)
