Giải thích các bước giải:
a.Ta có:
$\dfrac{25\cdot 7\cdot 19}{38\cdot 50}$
$=\dfrac{25\cdot 7\cdot 19}{2\cdot 19\cdot 2\cdot 25}$
$=\dfrac7{2\cdot 2}$
$=\dfrac74$
b.Ta có:
$\dfrac{29\cdot 7-29}{4\cdot (-33)}$
$=\dfrac{29\cdot (7-1)}{-4\cdot 33}$
$=\dfrac{29\cdot 6}{-4\cdot 11\cdot 3}$
$=\dfrac{29\cdot 2\cdot 3}{-2\cdot 2\cdot 11\cdot 3}$
$=\dfrac{29}{-2\cdot 11}$
$=\dfrac{29}{-22}$
c.Ta có:
$\dfrac{315}{125}$
$=\dfrac{315:5}{125:5}$
$=\dfrac{63}{25}$
d.Ta có:
$\dfrac{3510-135}{4680-180}$
$=\dfrac{135(26-1)}{180(26-1)}$
$=\dfrac{135\cdot 25}{180\cdot 25}$
$=\dfrac{135}{180}$
$=\dfrac{135:45}{180:45}$
$=\dfrac34$