The given equation is a linear equation in one variable, x. To solve the equation, we need to combine like terms on the left side of the equation. Adding the coefficients of x, we get 3x + 5x = 8x. So, the equation becomes 8x + 9 = 25. To isolate x, we subtract 9 from both sides of the equation, which gives us 8x = 16. Finally, we divide both sides of the equation by 8, and we find that x = 2.