Correct Answer:  The purchase price of the shirt is Tk. 90.

Explanation:

Let, the purchase price is Tk. x

Here, the gain = x of x% =x $\times$$\frac{x}{100}$=$\frac{x^{2}}{100}$ Tk

According to the question,

$\frac{x^{2}}{100}$ + x = 171

=> x$^{2}$ + 1OOx— 17100 = 0

=> x$^{2}$ + 190x – 90x – 17100 = 0

=> x(x + 190) – 90(x + 190) = 0

=> (x+190) (x-90) = 0

So, x = 90

Therefore, the purchase price is Tk. 9O