1. The problem is to understand the mapping defined by the expression $X - 2 - 3X$. 2. First, combine like terms: $X - 3X = -2X$. 3. Substitute back: $-2X - 2$. 4. So the mapping simplifies to $f(X) = -2X - 2$. 5. This is a linear function where the output depends on the input $X$ multiplied by $-2$ and then decreased by $2$. 6. For example, if $X=1$, then $f(1) = -2(1) - 2 = -4$. 7. This function can be graphed as a straight line with slope $-2$ and y-intercept $-2$.