1. The problem is to add $x$ to $x$. 2. The formula for addition of like terms is $a + a = 2a$. 3. Since both terms are $x$, we add their coefficients: $1 + 1 = 2$. 4. Therefore, $x + x = 2x$. 5. This means adding $x$ to $x$ results in $2x$.