Code for solving simultaneous differential equations

Can someone help me with the code for solving two simultaneous differential equations ( Preferably RK method of order 4 ) in the form of this

• dP/dt = a*P + b*Q
• dQ/dt = c*P + d*Q

Initial conditions are P(0)=2 and Q(0)=1

Where a,b,c,d are constants ( I know the values of a,b,c,d just want to know in a general case )

My actual problem is much more complicated than this ( I am trying to solve a fluid dynamics problem with 10 such simultaneous differential equations )

Thanks in advance