If 7 is added to the sum of digits of a two-digit number, the summation will be three times the tens digit, If 18 is subtracted from the original number, its digits are reversed. Find the number.

A street vendor sells oranges throughout the year. During the off-seasons, he sells each orange for Tk 8 but his cost price is Tk 11 per orange. During the on-seasons, his cost price drops to Tk 6 per orange and he sells each one for Tk 10. His fixed monthly overhead costs are Tk 3,000. In a particular year, he sells 1,800 oranges during the 4 off-season months and must sell enough oranges during the remaining 8 on-season months to end the year with an overall profit of at least Tk. 5,000. What is the minimum number of oranges he must sell during on-season to achieve this?

The speed of a boat in still water is 10 km per hour. If it can travel 24 km downstream and 14 km in the upstream in equal time, calculate the speed of the flow of stream.

A wedding organizer distributed bonuses equally among his staff. If 5 more staff had been present, each person would have received Tk 50 less. But if 5 fewer staff had shown up, each person would have received Tk 75 more. How many staff members actually worked at the wedding?

There are 3 doors and 6 windows in a house. Each of the doors is 2 meters long and 1.25 meters wide and each of the windows is 1 meter long and 1.25 meters wide. How many pieces of 5 meters long and 0.60 meters wide wood are required to make the doors and windows?