`a. 0,3x-\frac{1}{4}=\frac{1}{4}`
`=>0,3x=\frac{1}{2}`
`=>x=\frac{10}{2.3}`
`=>x=5/3`
`b. \frac{3}{4}.x=(\frac{4}{3})^26:(\frac{4}{3})^25`
`=>\frac{3}{4}.x=4/3`
`=>x=4/3:3/4`
`=>x=16/9`
`c. (\frac{9}{11})^19:x=(\frac{9}{11})^18`
`=>x=(\frac{9}{11})^19:(\frac{9}{11})^18`
`=>9/11`
`d. x:(\frac{5}{7})^17=(\frac{7}{5})^19`
`=>x=\frac{7^19}{5^19}.\frac{5^17}{7^17}`
`=>x=\frac{7^19 .5^17}{5^19 .7^17}`
`=>x=\frac{7^2}{5^2}=\frac{49}{25}`
