This question hints at the approach by instructing you to leave the answer in the form lg a/lg b. Observe the two simultaneous equations and you will notice that the first equation is in the form of integers with an unknown power. This is an indication to log both sides of the equation.

Recall the logarithmic rules, namely the product rule and power rule. A good practice once you have obtained an answer would be to substitute the values obtained back into both starting equations to check if they satisfy both equations.