These sentences can be rewritten as the mathematical equations, d-5=3(j-5) and d+2=2(j+2). Solving both equations for d gives, d=3j -10 and d= 2j +2. You can now set the right hand side of these equations equal to each other and solve for j to find that j=12. Substituting 12 for j in any of the equations, gives you Dave's age, d =26.
