Bài 1: 

a: 67,5:9=7,5

9919:53=?

\(\left(1314-808\right):23+1995\)

\(=506:23+1995\)

\(=22+1995\)

\(=2017\)

= 506 :23 + 1995

= 22 +1995

=  2017 .

dung 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000% 

nhớ k cho mình nha

=2018^2*2018*2017

=2018^3*2017

Bài 4: 

a: \(\Leftrightarrow n-1\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{2;0;6;-4\right\}\)

senpai đang viết j vậy

\(\dfrac{2n-1}{n+2}=\dfrac{2\left(n+2\right)}{n+2}-\dfrac{5}{n+2}=2-\dfrac{5}{n+2}\)

Để \(\dfrac{5}{n+2}\) ∈ Z

⇒ \(\left(n+2\right)\) ∈ \(Ư\left(5\right)=\left(1;-1;5;-5\right)\)

⇒ \(n\) ∈ \(\left(-1;-3;3;-7\right)\)

a: =100x54-100x(-6)

=100x60

=6000

b: =99(123-56+66-123)=990

c: =547x(1+103-4)=54700

d: =-76x10=-760

3 phút 15 giây x 6 = 18 phút 90 giây = 19 phút 30 giây

a)                                                     b) 

       ^x\(\begin{matrix}\text{3 phút 15 giây}\\6\\\overline{\text{19 phút 30 giây}}\end{matrix}\)                             ⁺\(\begin{matrix}\text{9 giờ 25 phút}\\\text{5 giờ 45 phút}\\\overline{\text{15 giờ 10 phút }}\end{matrix}\)

c)

        ^x\(\begin{matrix}235,05\\4,2\\\overline{987,21}\end{matrix}\)

d)

    \(91,25\)         \(25\)

    \(75\)             \(3,65\)

     \(162\)    

     \(150\)

       \(125\)

           \(0\)

c: \(\Leftrightarrow n+2\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-1;-3;3;-7\right\}\)

d: \(\Leftrightarrow n+2\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{-1;-3;0;-4;2;-6\right\}\)

a: \(\Leftrightarrow n-1\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{2;0;6;-4\right\}\)