Answer:
<em>The cost price of the article was Nu 1,000</em>
<em>The original selling price was Nu 1,120</em>
<em>The second selling price was Nu 1,200</em>
Step-by-step explanation:
<u>System of Equations</u>
Let's call:
x = Original selling price of the article
y = Cost of the article
The first condition implies that the difference between the selling price and the cost price (the profit) is 12%. Recall the profit % is always calculated with respect to the cost, that is, the profit at the first condition is:
0.12y = Original profit
Setting up the equation, we have:

The second condition states the selling price is 80 Nu more than before, that is:
x+80= Second selling price of the article
y = Cost of the article (it doesn't change)
The profit of this condition is 20%, thus:
0.2y = Second profit
This produces a second equation:

Let's put both equations together to form a system of equations:


Operating on both equations:


Equating both equations, we have an equation with only y's:

Subtracting 1.2y on each side:

Operating:

Solving:

a)
The cost price of the article was Nu 1,000
b) The selling price of the article will be calculated in both cases:
Original selling price: x=1.12y= 1.12*1000=1,120
The original selling price was Nu 1,120
The second selling price was x+80=1,200
The second selling price was Nu 1,200