Bài 1 :
a) \(2^3.26+2^3.74\)
\(=2^3.\left(26+74\right)\)
\(=8.100\)
\(=800\)
b) \(\left(-15\right)+14+\left(-85\right)\)
\(=14+\left[\left(-85\right)+\left(-15\right)\right]\)
\(=14+-100\)
\(=-86\)
c) \(12\div\left\{400\div\left[500-\left(125+25.7\right)\right]\right\}\)
\(=12\div\left\{400\div\left[500-\left(125+175\right)\right]\right\}\)
\(=12\div\left\{400\div\left[500-300\right]\right\}\)
\(=12\div\left\{400\div200\right\}\)
\(=12\div2\)
\(=6\)
Bài 2 :
a) \(3x+12=45\)
\(3x=45-12\)
\(3x=33\)
\(x=33\div3\)
\(x=11\)
b) \(\left(x-5\right)\div7=2020^0+3\)
\(\left(x-5\right)\div7=4\)
\(x-5=7.4\)
\(x-5=28\)
\(x=28+5\)
\(x=33\)
c) Theo đề bài :
x chia hết cho 15
x chia hết cho 200
x chia hết cho 35
\(\Rightarrow x\in BCNN\left(15;35;200\right)\)
\(\left[{}\begin{matrix}15=3.5\\35=5.7\\200=2^4.3.5^2\end{matrix}\right.\)
\(BCNN\left(15;35;20\right)=3.5.7.2=210\)
\(\Rightarrow x=210\)
bài cuối làm tương tự nhé
