I can write that equation as $3x + 7 = -8$. First, I can subtract $7$ from both sides of the equation to get rid of the constant term. That gives me $3x = -15$. Next, I can divide both sides by $3$ to get rid of the coefficient of $x$. That gives me $x = -5$. 
If $x$ is tripled and then increased by $7$, the result is $-8$. What is the value of $x$?