Answer:x= [tex]\frac{b}{3+9y}[/tex] .Step-by-step explanation:Given : b = 3x + 9xy.To find : Solving the equation for x.Solution : We have given b = 3x + 9xy.Taking common 3x from right hand sideb = 3x ( 1 + 3y).On dividing both sides by 1 + 3y .[tex]\frac{b}{1+3y}[/tex] = 3x On dividing both sides by 3[tex]\frac{b}{(3+9y)}[/tex] = x .Therefore, x =[tex]\frac{b}{(3+9y)}[/tex] .