To solve the expression $\frac{5}{4} + \frac{3}{5} - \frac{9}{10}$, follow these steps:

1. Find a common denominator: The denominators are 4, 5, and 10. The least common denominator (LCD) is 20.

2. Convert each fraction to have the denominator of 20: $\frac{5}{4} = \frac{5 \times 5}{4 \times 5} = \frac{25}{20}$ $\frac{3}{5} = \frac{3 \times 4}{5 \times 4} = \frac{12}{20}$ $\frac{9}{10} = \frac{9 \times 2}{10 \times 2} = \frac{18}{20}$

3. Add and subtract the fractions: $\frac{25}{20} + \frac{12}{20} - \frac{18}{20} = \frac{25 + 12 - 18}{20} = \frac{19}{20}$

The result of the expression is: $\frac{19}{20}$

Would you like further details or have any questions?

Here are 5 related questions to deepen your understanding:

1. How do you find the least common denominator for a set of fractions?
2. What is the process for converting fractions to have a common denominator?
3. How can you simplify fractions after performing addition or subtraction?
4. What happens if you add or subtract fractions with different denominators without finding a common denominator?
5. How would you convert a fraction like $\frac{19}{20}$ into a decimal?

Tip: Always double-check your final answer by simplifying the fractions to their lowest terms, if possible.