To find the constant of variation, we need to identify the relationship between the variables in each equation. For direct variation, the constant of variation \( k \) is the coefficient of \( x \) in the equation \( y = kx \). For inverse variation, the constant is found by multiplying the variables together, \( xy = k \).
For equation 7, \( y = 3x \), the constant of variation \( k \) is directly given as 3.
For equation 9, \( \frac{y}{x} = 5 \), the constant of variation \( k \) is 5.
For equation 11, \( y = \frac{3}{5}x \), the constant of variation \( k \) is \(\frac{3}{5}\).
Step 1: Constant of Variation for Equation 7
For the equation \( y = 3x \), the constant of variation \( k \) is directly given as:
\[
k_7 = 3
\]
Step 2: Constant of Variation for Equation 9
For the equation \( \frac{y}{x} = 5 \), we can express this as \( y = 5x \). Thus, the constant of variation \( k \) is:
\[
k_9 = 5
\]
Step 3: Constant of Variation for Equation 11
For the equation \( y = \frac{3}{5}x \), the constant of variation \( k \) is:
\[
k_{11} = \frac{3}{5} = 0.6
\]
Final Answer
The constants of variation are:
\[
\boxed{k_7 = 3}, \quad \boxed{k_9 = 5}, \quad \boxed{k_{11} = 0.6}
\]