Subtract 10 from both sides.
$3x+10-10=25-10$

Divide both sides by $3$.

$x=5$

Start by dividing both sides by $5$.

When you have found a solution, substitute it into the equation for $x$ to check your answer.

Isolate $x$ on one side of the equation. When you have found an answer, be sure to check it.

$x=16$