Answer:

Explanation:
The missing number in the denominator would be 10, because 4 divided by 5 is 0.8, and 8 divided by 10 is also 0.8, making them congruent to one another.
You can also simplify/reduce
by divided the numerator and the denominator by its common factor, 2. This gives you the fraction of
, proving they are equivalent to one another.