1. The problem is to simplify and combine algebraic expressions involving variables $X1$, $X2$, $X3$, and $X4$ with fractional coefficients. 2. We start with the expression: $$\frac{X1}{10} + \frac{X2}{5} + \frac{X3}{5} + \frac{X4}{2}$$ 3. To add these fractions, we find the least common denominator (LCD). The denominators are 10, 5, 5, and 2. The LCD is 10. 4. Convert each term to have denominator 10: $$\frac{X1}{10} + \frac{\cancel{2}X2}{\cancel{2}10} + \frac{\cancel{2}X3}{\cancel{2}10} + \frac{5X4}{5 \times 2} = \frac{X1}{10} + \frac{2X2}{10} + \frac{2X3}{10} + \frac{5X4}{10}$$ 5. Now combine all terms over the common denominator: $$\frac{X1 + 2X2 + 2X3 + 5X4}{10}$$ 6. This is the simplified form of the second expression. 7. The same method applies to other expressions: find the LCD, convert each term, then combine. Final answer: $$\frac{X1 + 2X2 + 2X3 + 5X4}{10}$$