I don't know how to solve this system of equations in $k_1,k_2$

Question

This is the system I need to solve for $k_1, k_2$.

$k_1 = \lambda y_n + \frac{\lambda h}{4}k_1 -\frac{\lambda h}{4}k_2 $

$ k_2 = \lambda y_n + \frac{3\lambda h}{12}k_1 + \frac{5\lambda h}{12}k_2$

I'd also like to know if there's any symbolic calculator I can use to solve this type of problem since manually it becomes very tedious.

Answer 1

Using @manooooh answer, the answer is:

Thanks everyone that contributed