Chapter P - Section P.1 - Algebraic Expressions, Mathematical Models, and Real Numbers - Exercise Set - Page 18: 125

$5x-2x$ $3x$

The product of $5$ and $x$ is just the two multiplied together: (5x). Twice the number $x$ is just $2$ times $x$: (2x). To find the difference between them, you subtract: $((5x)-(2x))$, which simplifies to $3x$.