Since the variation is generic, then we have an equation of the form:
![y = kx](https://img.qammunity.org/2019/formulas/mathematics/college/1irueestzcfe1jy6nsxceq3bgce3a8o4zs.png)
Where,
k: proportionality constant.
We must find the value of k.
For this, we use the following data:
x = 2 then y = 6
We have then:
![6 = k2](https://img.qammunity.org/2019/formulas/mathematics/high-school/7gz5031jatowmy7ru6o2mn7p0yut5f0aha.png)
Clearing k we have:
![k = 3](https://img.qammunity.org/2019/formulas/mathematics/high-school/k4bwrotlr5klkrm3nwy0bshfiho0z2pe34.png)
Then, the equation is:
![y = 3x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/teh3e8j8bxy4mgdjtfjqfbhb1m7bxubon2.png)
Substituting for x = 7 we have:
![y = 3 (7)](https://img.qammunity.org/2019/formulas/mathematics/high-school/ke74cq8t3skvvv5e56trm1df31p8qd2dlh.png)
![y = 21](https://img.qammunity.org/2019/formulas/mathematics/high-school/glsk1z9lg4f2t6r8wph1bi6k903zfft90l.png)
Answer:
The value of y for x = 7 is:
![y = 21](https://img.qammunity.org/2019/formulas/mathematics/high-school/glsk1z9lg4f2t6r8wph1bi6k903zfft90l.png)