a) x-\(\left(\frac{50x}{100}+\frac{25x}{200}\right)\)=\(11\frac{1}{4}\)
<=>x - \(\frac{1}{2}x-\frac{1}{8}x\)=\(\frac{11.4+1}{4}\)
<=>\(\frac{3}{8}x=\frac{45}{4}\)
<=>x=\(\frac{45}{4}:\frac{3}{8}\)
<=>x=30
Vậy x=30
c) (x-5).\(\frac{30}{100}\)=\(\frac{20x}{100}+5\)
<=>(x-5).\(\frac{3}{10}\)=\(\frac{x}{5}\)+5
<=>\(\frac{3x}{10}-\frac{15}{10}=\frac{x}{5}+5\)
<=>\(\frac{3x}{10}-\frac{x}{5}=5+\frac{15}{10}\)
<=>\(\frac{x}{10}=\frac{13}{2}\)
<=>x=\(\frac{13.10}{2}\)
<=>x=65
Vậy: x=65