To express the given proportion, 0.55, as a fraction, we can follow these steps:

1. Write 0.55 as a fraction:
   $0.55 = \frac{55}{100}$

2. Simplify the fraction by finding the greatest common divisor (GCD) of 55 and 100.
   The GCD of 55 and 100 is 5.

3. Divide both the numerator and the denominator by 5:
   $\frac{55 \div 5}{100 \div 5} = \frac{11}{20}$

Therefore, the fraction of the total number of apps on Gabi's phone that are video apps is $\frac{11}{20}$.

Would you like more details or have any questions on this? Here are some related questions for further exploration:

1. How do you simplify a fraction?
2. How do you convert a decimal into a fraction?
3. What is the concept of proportions in mathematics?
4. What is the greatest common divisor (GCD) and how do you find it?
5. How can you express other decimals (like 0.75 or 0.33) as fractions?

Tip: When simplifying fractions, always divide both the numerator and denominator by their greatest common divisor (GCD).