Let $d$ be TNYWR.

Lawrence runs $\frac{d}{2} \mathrm{~km}$ at an average speed of 8 minutes per kilometre.

George runs $\frac{d}{2} \mathrm{~km}$ at an average speed of 12 minutes per kilometre.

How many minutes more did George run than Lawrence?

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Observe that the time it takes to run a given distance (in minutes) is the product of the distance (in kilometres) and the rate (in minutes per kilometre).

The time it took Lawrence to complete the run was $8 \times \frac{d}{2}=4 d$ minutes.

The time it took George to complete the run was $12 \times \frac{d}{2}=6 d$ minutes.

Therefore, it took George $6 d-4 d=2 d$ minutes longer than Lawrence to complete the run.

Substituting $d=52$, it took George 104 minutes longer than Lawrence to complete the run.