the variable y varies directly as x. when x =20, y= 12 what is the value of y when x = 15a:7b:9c:18d:25

To direct variations use a rule of three, as follow:
[tex]\begin{gathered} \frac{?}{12}=\frac{15}{20} \\ \\ ?=12*\frac{15}{20} \\ \\ ?=\frac{180}{20} \\ \\ ?=9 \end{gathered}[/tex]Then, when x=15, y is 9