Bài 5:
a) \(\left(273+49\right)-173\)
\(=273+49-173\)
\(=\left(273-173\right)+49\)
\(=100+49\)
\(=149\)
b) \(678-\left(578+62\right)\)
\(=678-578-62\)
\(=\left(678-578\right)-62\)
\(=100-62\)
\(=38\)
c) \(97-94+91-88+...+7-4\)
\(=\left(97-94\right)+\left(91-88\right)+...+\left(7-4\right)\)
\(=3+3+3+...+3\) (16 số 3)
\(=3\cdot16\)
\(=48\)
d) \(110-108+106-104+102-...+2-0\)
\(=\left(110-108\right)+\left(106-104\right)+...+\left(2-0\right)\)
\(=2+2+2+...+2\) (28 số 2)
\(=28\cdot2\)
\(=56\)
4:
a: =938-38+172-72
=900+100
=1000
b: =763-100=663
c: =2317-317+346+54
=2000+400
=2400
d: =382-82+181+119
=300+300
=600
