Alaa calculates the sum of the first ^@n^@ positive integers and finds that the sum is ^@3659^@. If she has counted one integer twice, which one is it?

One ticket to a show costs SR10. Maboutou buys a total of 5 tickets for the show using a coupon that gives her a 15% discount. Mohammed buys 7 tickets, using a coupon that gives a 20% discount. How much more did Mohammed pay than Maboutou?

The front wall of a factory as shown below has to be painted. The area of the entrance shown in grey does not need to be painted. If the cost of painting is SR40 per square m, find the total cost for painting the entire wall.

Saad bought a total of 19 hens and ducks. He got a discount of SR0.40 for each hen and a discount of SR1.50 for each duck. He saved SR19.70 in total. How many hens did he buy?