Call the two offers offer A and B respectively.
For offer A, the list price is 5000 pesos with a 15% discount. So you will pay:
For offer B, the list price is 5200 with a 20% discount. So you will pay:
So the first deal is costing 4250 pesos and second one costs 4160 pesos.
Hence the second deal is better by 4250-4160= 90 pesos.
The second deal is the better deal by 90 pesos.