We want to solve the equation :
[tex]\displaystyle{ \frac{3}{4}(x+3)=9 [/tex]
first, multiply both sides by 4:
[tex]\displaystyle{ \cancel{4} \cdot \frac{3}{ \cancel 4 }(x+3)=4\cdot 9 [/tex]
[tex]\displaystyle{ 3(x+3)=36[/tex]
divide both sides by 3:
[tex]x+3=12[/tex]
add -3 to both sides:
[tex]x=9[/tex]
Answer: x=9