We know that :
[tex]\bigstar \ \ \boxed{\sf{sin\theta = \dfrac{Opposite \ Side}{Hypotenuse}}}[/tex]
From the figure, We can notice that :
↔ Opposite side of Angle Q is 9 units
↔ Hypotenuse is 15 units
[tex]\sf{\implies sinQ = \dfrac{9}{15}}[/tex]
[tex]\sf{\implies sinQ = \dfrac{3}{5}}[/tex]
