Answer:
126
Step-by-step explanation:
By cyclic quadrilateral theorem:

At a restaurant Mike and his three friends that means that there was four people splitting the bill. If each of them paid $13 then the bill was $52
4 * 13 = $52
multiply 40 by 30% to find the discount then subtract
40 * 0.30 = 12
40-12 = 28
they would cost $28
Answer: The percent gain was 25%.
Step-by-step explanation:
Given, Cost price of lot = $1,200
Selling price of lot = $1,500
The percent gain = 
⇒ Percent gain =

Hence, the percent gain was 25% based on his purchase.