Đáp án:
$\begin{array}{l}
70)\\
a)390 - \left( {x - 7} \right) = 169:13\\
\Rightarrow 390 - x + 7 = 13\\
\Rightarrow x = 13 - 397\\
\Rightarrow x = - 384\\
\text{Vậy}\,x = - 384\\
b)\left( {x - 140} \right):7 = {3^3} - {2^3}.3\\
\Rightarrow \left( {x - 140} \right):7 = 27 - 8.3\\
\Rightarrow \left( {x - 140} \right):7 = 27 - 24 = 3\\
\Rightarrow x - 140 = 3.7 = 21\\
\Rightarrow x = 21 + 140\\
\Rightarrow x = 161\\
\text{Vậy}\,x = 161\\
c)x - 6:2 - \left( {48 - 24} \right):2:6 - 3 = 0\\
\Rightarrow x - 3 - 24:2:6 - 3 = 0\\
\Rightarrow x - 3 - 2 - 3 = 0\\
\Rightarrow x = 8\\
\text{Vậy}\,x = 8\\
d)x + 5.2 - \left( {32 + 16.3:6 - 15} \right) = 0\\
\Rightarrow x + 10 - \left( {32 + 8 - 15} \right) = 0\\
\Rightarrow x + 10 - 25 = 0\\
\Rightarrow x = 25 - 10 = 15\\
\text{Vậy}\,x = 15\\
71)\\
a)\left( {{6^2} + {7^2} + {8^2} + {9^2} + {{10}^2}} \right)\\
- \left( {{1^2} + {2^2} + {3^2} + {4^2} + {5^2}} \right)\\
= \left( {{6^2} - {1^2}} \right) + \left( {{7^2} - {2^2}} \right) + .. + \left( {{{10}^2} - {5^2}} \right)\\
= \left( {6 - 1} \right).\left( {1 + 6} \right) + \left( {7 - 2} \right).\left( {2 + 7} \right) + ...\\
+ \left( {10 - 5} \right).\left( {10 + 5} \right)\\
= 5.\left( {1 + 6} \right) + 5.\left( {2 + 7} \right) + ... + 5.\left( {10 + 5} \right)\\
= 5.\left( {1 + 6 + 2 + 7 + 3 + 8 + 4 + 9 + 10 + 5} \right)\\
= 5.\frac{{\left( {10 + 1} \right).10}}{2}\\
= 275\\
b)\left( {{{125}^3}{{.7}^5} - {{175}^5}:5} \right):{2001^{2002}}\\
= \left( {{5^{3.3}}{{.7}^5} - {{\left( {{5^2}.7} \right)}^5}:5} \right):{2001^{2002}}\\
= \left( {{5^9}{{.7}^5} - {5^{10}}{{.7}^5}:5} \right):{2001^{2002}}\\
= 0:{2001^{2002}}\\
= 0\\
c){16.64.8^2}:\left( {{4^3}{{.2}^5}.16} \right)\\
= {2^4}{.2^6}{.2^6}:\left( {{2^6}{{.2}^5}{{.2}^4}} \right)\\
= {2^{16}}:{2^{15}}\\
= 2
\end{array}$
