Final answer:
The original price of the burger, before the discount, was 50 pesos.
Step-by-step explanation:
To find the original price of the burger before the discount, we need to subtract the discount amount from the discounted price. The customer paid 50 pesos after a discount of 20 pesos, so the discounted price is 50 + 20 = 70 pesos. To find the original price, we need to subtract the discount from the discounted price: 70 pesos - 20 pesos = 50 pesos. Therefore, the original price of the burger was 50 pesos.