pleasee...

if she takes x hrs originally, then now she wants to finish the task in x-(1/4)x hrs

 i.e. 3x/4 hrs

so her speed must be 4/3 times the original speed.

so if the spped was y hrs, then it must now be 4y/3

so an increase of y/3 needs to be done to her speed

i.e.

in y an increment of y/3 is reqd

we can  find for 100 easily.

 that is the percentage increase.