Chapter P - Section P.1 - Algebraic Expressions, Mathematical Models, and Real Numbers - Exercise Set - Page 18: 126

$6x-(-2x)$ $8x$

The product of 6 and x is simply them multiplied together: $6x$. Two times $x$ is $2x$. Negative two times $x$ is $-2x$. The difference between $6x$ and $-2x$ is the second subtracted from the first: $6x-(-2x)$, which equals $8x$.