The fisrt problem is answerd by setting up solving the equation . It's a second order equation.
To solv the second problem, you start this way:
Allway isolate one of the unknown variables so you get an equation for it. In this case, you can isolate y by dividing the first equation by x. You'll get
which also tells you that x isn't zero.
By insertion into the second equation you'll get
That's a second order equation too. But I guess you can see that stuff for yourself