Given P, express q in terms of p and r

Question

Given that P = 2q – r, express q in terms of p and r 
                         q + 3r 

Answer 1

p(q + 3r) = 2q – r
pq + 3pr = 2q – r
pq -2q = -r – 3pr
q(p-2)=-r-3pr
q=-r-3pr
      p-2