Rút gọn biểu thức \(A = \dfrac{{3.\left( { - 4} \right).60 - 60}}{{50.20}}\) ta được

\(\dfrac{a}{b} = \dfrac{{a.m}}{{b.m}}\,\) 

\(\dfrac{a}{b} = \dfrac{{a + m}}{{b + m}}\,\)  

\(\dfrac{a}{b} = \dfrac{{ - a}}{{ - b}}\,\)            

\(\dfrac{a}{b} = \dfrac{{a:n}}{{b:n }}\) với \(n\) là ước chung của \(a;b.\)

$\left\{ {1; - 1} \right\}$         

\(\left\{ 2 \right\}\)  

\(\left\{ {1;2} \right\}\)

\(\left\{ {1;2;3} \right\}\)

\(a = 3,b =  - 259\)                

\(a =  - 3,b =  - 259\)  

\(a = 3,b = 259\)

\(a =  - 3,b = 259\)

$180$ 

\(500\)  

\(750\) 

\(450\)

\(\dfrac{{ - 2}}{4}\) 

\(\dfrac{{ - 15}}{{ - 96}}\)  

\(\dfrac{{13}}{{27}}\)

\(\dfrac{{ - 29}}{{58}}\)

\(\dfrac{{16}}{{56}};\dfrac{{ - 35}}{{56}}\)        

\(\dfrac{{16}}{{56}};\dfrac{{35}}{{56}}\)  

\(\dfrac{{16}}{{56}};\dfrac{{35}}{{ - 56}}\)      

\(\dfrac{{ - 16}}{{56}};\dfrac{{ - 35}}{{56}}\)

\(\dfrac{1}{2}\)                    

\(\dfrac{6}{8}\)          

\(\dfrac{3}{4}\)                 

\(\dfrac{{ - 3}}{4}\)