2 : \(buổi \) \(sáng\) \(bán\) \(dc :\)

\((360 - 142 : 2 =109 l\)

\(buổi\) \(chiều\) \(bán\) \(dc :\)

\(360 - 109 = 251 l\)

\(1,\)

\(a,x\times\dfrac{3}{9}=\dfrac{9}{15}\)            \(b,x:\dfrac{1}{2}=\dfrac{5}{6}\)

\(x=\dfrac{9}{15}:\dfrac{3}{9}\)                    \(x=\dfrac{6}{5}\times\dfrac{1}{2}\)

\(x=\dfrac{81}{45}=\dfrac{9}{5}\)                  \(x=\dfrac{6}{10}=\dfrac{3}{5}\)

\(2,\) có bạn làm rồi nhé ;>

\(3,\)

\(a,\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\left(\dfrac{3}{4}\times\dfrac{2}{9}\right)=\dfrac{7}{12}+\dfrac{1}{6}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{7+2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

\(b,\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\left(\dfrac{4}{15}:\dfrac{2}{5}\right)=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{8-6}{9}=\dfrac{2}{9}\)

a.x=9/15:3/9

x=9/5

b.x=5/6x1/2

x=5/12

2.ngày đầu bán được số dầu là:

360x2/5=144(l)

cửa hàng còn lại số dầu là:

360-144=216(l)

3.a.7/12+3/4x2/9

=7/12+1/6

=7/12+2/12

=9/12=3/4

a) Ta có: \(\left(2x-3\right)-\left(x-5\right)=\left(x+2\right)-\left(x-1\right)\)

\(\Leftrightarrow2x-3-x+5=x+2-x+1\)

\(\Leftrightarrow x+2=3\)

hay x=1

Vậy: x=1

b) Ta có: \(2\left(x-1\right)-5\left(x+2\right)=-10\)

\(\Leftrightarrow2x-2-5x-10=-10\)

\(\Leftrightarrow-3x=-10+10+2=2\)

hay \(x=-\dfrac{2}{3}\)

Vậy: \(x=-\dfrac{2}{3}\)

a, (2x - 3) - (x - 5) = (x + 2) - (x - 1)

 2x - 3 - x + 5 = x + 2 - x + 1

(2x - x) + (-3 + 5) = (x - x) + (2 + 1)

x + 2 = 3

x = 1

a) \(\dfrac{x.2}{-15}=\dfrac{-5}{3}\)

\(\dfrac{x.2}{-15}=\dfrac{25}{-15}\)

x.2=25

x=12,5

b) \(\dfrac{x-1}{-12}=\dfrac{-3}{x-1}\)

(x-1)²=-3.(-12)

(x-1)²=36 

⇒(x-1)²\(\Rightarrow\left[{}\begin{matrix}x-1=6\\x-1=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=7\\x=-5\end{matrix}\right.\)

Vì \(\left(x-\frac{1}{5}\right)^2\ge0\).Dấu "=" xảy ra khi \(x=\frac{1}{5}\)

\(\Rightarrow A=\left(x-\frac{1}{5}\right)^2+\frac{11}{15}\ge\frac{11}{15}\)

Nên GTNN của A là \(\frac{11}{15}\) xảy ra khi \(x=\frac{1}{5}\)

Cảm ơn các bạn nhiều nha

a) \(x+\dfrac{4}{15}=\dfrac{4}{12}\)

\(x=\dfrac{4}{12}-\dfrac{4}{15}\)

\(x=\dfrac{20}{60}-\dfrac{16}{60}\)

\(x=\dfrac{1}{15}\)

b) \(x-\dfrac{5}{8}=1\dfrac{2}{3}\)

\(x-\dfrac{5}{8}=\dfrac{5}{3}\)

\(x=\dfrac{5}{3}+\dfrac{5}{8}\)

\(x=\dfrac{40}{24}+\dfrac{15}{24}\)

\(x=\dfrac{55}{24}\)

\(a,\Rightarrow1485,925-x-225=755\)

\(\Rightarrow1485,925-x=755+225\)

\(\Rightarrow1485,925-x=980\)

\(\Rightarrow x=1485,925-980\)

\(\Rightarrow x=505,925\)

\(b,\Rightarrow\left(9-5,34\right):x=3\)

\(\Rightarrow3,66:x=3\)

\(\Rightarrow x=3,66:3\)

\(\Rightarrow x=1,22\)