Let us assume the original price of the shirt = x
Let us assume the sale price of the shirt = y
20x/100 = y
x/5 = y
x = 5y
Now the second equation that we get is
x = y + 5
5y - y = 5
4y = 5
y = 5/4
Now putting the value of y in the first equation we get
x = 5y
= 5 (5/4)
= 25/4
= 6 1/4
Then we can say that the original price of the shirt was 6 1/4. The main trick of this problem lies in the words that have been used in the question. It is important to understand the question first before starting to solve the problem.