There are $850000$ users on an educational platform. On average, one user uses the platform $11$ times per month. There are two types of users: college and university students: the college ones use the platform $7$ times per month and the university one $13$ times per month. How many are college users?
I have tried to work the solution out by creating equations but I think I am missing something as I can't produce enough relations to work with.
Thank you in advance!!
$\frac{x(7) + (850000-x)13}{850000} = 11,$ where $x$ is the number of college users.