A city has a population of 38,802,500 people. Esitmate this population to the nearest ten million

Can someone me with these two circle theorem questions asap?

Complete each statement from the information given and the triangle criterion you used. if the triangles cannot be shown to be congruent, leave the box for the second triangle blank and choose for reason “cannot be determined.” carbon - regular hexagon. ∆can ≅ ∆ by

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9