Câu 2. Tính S=2x-y+z biết: x:y:z=3:4:5 và x+y-z=28

1. **Express variables in terms of a common factor:** Since , we can write: * * * (where k is a constant)2. **Substitute into the given equation:** Substitute the expressions for x, y, and z into the equation : 3. **Solve for k:** Simplify the equation: Therefore, 4. **Calculate x, y, and z:** * * * 5. **Calculate S:** Substitute the values of x, y, and z into the expression for S: Therefore, .