\(\dfrac{17}{6}+\dfrac{26}{-12}-\dfrac{-13}{39}\)
\(=\dfrac{17}{6}-\dfrac{13}{6}+\dfrac{1}{3}\)
\(=\dfrac{4}{6}+\dfrac{1}{3}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}\)
\(=1\)

AB, BC, CA

`7/19*8/11-7/19*(-3)/11+12/19`

`=7/19*(8/11-(-3)/11)+12/19`

`=7/19*1+12/19`

`=7/19+12/19`

`=19/19=1`

\(\dfrac{38}{45}-\left(\dfrac{8}{45}-\dfrac{17}{51}-\dfrac{3}{11}\right)\)
\(=\dfrac{38}{45}-\dfrac{8}{45}+\dfrac{17}{51}+\dfrac{3}{11}\)
\(=\left(\dfrac{38}{45}-\dfrac{8}{45}\right)+\dfrac{1}{3}+\dfrac{3}{11}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{3}{11}\)
\(=\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\dfrac{3}{11}\)
\(=1+\dfrac{3}{11}\)
\(=\dfrac{11}{11}+\dfrac{3}{11}\)
\(=\dfrac{14}{11}\)

Ta có:
\(\dfrac{-34}{85}=\dfrac{-34:17}{85:17}=\dfrac{-2}{5}\)
\(\dfrac{26}{-65}=\dfrac{26:13}{-65:13}=\dfrac{-2}{5}\)
Do đó \(\dfrac{-34}{85}=\dfrac{26}{-65}\)

Giúp tui với 

Lời giải:
$\frac{2x}{15}=\frac{-4}{5}$

$x=\frac{-4}{5}: \frac{2}{15}=-6$

\(\dfrac{2x}{15}=-\dfrac{4}{5}\)

\(\Leftrightarrow2x.5=\left(-4\right).15\Leftrightarrow10x=-60\)

\(\Leftrightarrow x=-6\)

Lời giải:

Mỗi công nhân làm việc trong 1 giờ được số tiền là:

$1600000:6:4=\frac{200000}{3}$ (đồng)

12 người, làm việc trong 4 giờ được số tiền là:

$\frac{200000}{3}\times 12\times 4=3200000$ (đồng)