La mamá de Memo organiza un convivio para él y sus amigos por lo cual prepara 18 sándwiches, 24 vasos de refresco y 12 tamales. La mamá de Memo le dijo que vigile
que a sus amigos y a él les toquen el mayor número de sándwiches, vasos de refresco
y tamales sin que alguien agarre de más. ¿cuántos amigos tiene Memo si no sobró
nada? ¿cuánto de cada alimento comió cada quién?

30% profit

Step-by-step explanation:

The amount by which the shopkeeper reduced the advertised selling price = 20%

The resulting profit over the cost price = 4%

Let x represent the initial advertised selling price, and let y represent the new selling price, and let c represent the cost price, we have;

x - 20% of x = y

x - x × 20/100 = y

0.8·x = y

y = c + 4% of c = 1.04·c

∴ 0.8·x = 1.04·c

x = 1.04·c/0.8 = 1.3·c

x = 1.3·c = c + 0.3·c = c + 30% of c

x = c + 30% of c

From which we have that the initial advertised selling price, x = The cost price + 30% of the  cost price

Therefore, the initial advertised selling price = The cost price + 30%profit on   cost price.

The shopkeeper would have made 30% profit if the dress had then been sold at the original selling price.