When you divide a fraction by another fraction, it is the same thing as multiplying that fraction by its reciprocal.
The reciprocal is the 'flipped' version of a fraction where the numerator becomes the denominator and the denominator becomes the numerator.
for example, the reciprocal of 9/10 is 10/9
Knowing this information 4/5÷9/10 is the same as 4/5×10/9
Now we can solve...

Answer= 8/9