a) \(\frac{3}{5}\)< \(\frac{x}{6}\)< \(\frac{4}{5}\)
\(\frac{3\times6}{5\times6}\)< \(\frac{x\times5}{6\times5}\)< \(\frac{4\times6}{5\times6}\)
\(\frac{18}{30}\)< \(\frac{x\times5}{30}\)< \(\frac{24}{30}\)
18 < X x 5 < 24 => X x 5 = 20 => X = 4
b)\(\frac{3}{5}\)< \(\frac{2}{x}\)< \(\frac{4}{5}\)
\(\frac{3\times4}{5\times4}\)< \(\frac{2\times6}{x\times6}\)< \(\frac{4\times3}{5\times3}\)
\(\frac{12}{20}\)< \(\frac{12}{x\times6}\)< \(\frac{12}{15}\)
20 > X x 6 > 15 => X x 6 = 18 => X = 3
quy đồng mẫu số:
3/5=18/30;x/6=x×5/30;4/5=24/30
vậy x×5=19;20;21
mà x là số chia hết cho 5 nên x×5=20
x=20:5=4
ĐS:4
