Đáp án:
$\begin{array}{l}
a) - 7105 - \left( {155 - 7105} \right) + 355\\
= - 7105 - 155 + 7105 + 355\\
= 355 - 155\\
= 200\\
b)5 - 197 - 2015 - 20154\\
= 5 - 197 - 2015 - 20150 - 4\\
= - 22361\\
c)2004 - 15 + 54 - 2004 - 54\\
= \left( {2004 - 2004} \right) + \left( {54 - 54} \right) - 15\\
= - 15\\
d)1259 - 1409 - 12 + 1259 + 1409\\
= \left( {1259 - 1259} \right) + \left( { - 1409 + 1409} \right) - 12\\
= - 12\\
g) - 5 + \left( { - 37} \right) - 45 + 151 - 37 + 151\\
= \left( { - 5 - 45} \right) + \left( { - 37 - 37} \right) + 151 + 151\\
= - 50 - 74 + 302\\
= 178\\
l)254 - 49 - 75 + 254 - 175 + 549\\
= \left( {254 + 254} \right) + \left( { - 75 - 175} \right) + \left( {549 - 49} \right)\\
= 508 - 250 + 500\\
= 508 + 250\\
= 758\\
n)\left( {35 - 815} \right) - \left( {795 - 65} \right)\\
= 35 - 815 - 795 + 65\\
= 100 - 1610\\
= - 1510
\end{array}$
