Answer:
At least 6 shirts should be brought to avail a total reduction of Rs 40.
Step-by-step explanation:
The marked price of each shirt = Rs 28
Discount offered = 25%
So, 25% of marked price 28 = 
⇒Reduction on each shirt is Rs 7
Now, total amount reduction needed = Rs 40
So, number of shirts purchased = 
= 40 Rs /7 Rs = 5. 71 ≈ 6
So, at least 6 shirts should be brought to avail a total reduction of Rs 40.
Simply divide 61.50 by 3. You should be able to reach the answer that way
X+15 = 3x - 7 => 22 = 2x => x=11