1. The problem involves subtracting values from an expression involving $X_N$ and constants. 2. We start with the expression $180 - X - 130$. 3. According to the order of operations, subtraction is performed from left to right. 4. Simplify the constants first: $$180 - 130 = 50$$ 5. Substitute back: $$50 - X$$ 6. The simplified expression is $$50 - X$$. 7. This means we subtract $X$ from 50.