Round 745,829 to nearest ten thousand

Me write an equation for the interior angles of this triangle that uses the triangle sum theorem

How to do this , and can some one explain

Arestaurant charges $100 to rent its banquet room for an event. it also charges $15 to serve dinner to each guest. write an equation for the total cost of the banquet room in terms of the number of guests. deine your variables. what is the total cost of the banquet room for 20 guests?