17.URGENT!
I need help.

What is the approximate circumference of the circle shown below?

For f(x)=2x+1 and g(x)= x^2 -7, find (f•g)(x)

Arley is building a model of a city map. in one part of the city, three roads form a right triangle, which harley draws as triangle abc, with the following measures: m∠b=90° and m∠a=30°. in his scale model, the hypotenuse of triangle abc, ac¯¯¯¯¯¯¯¯, has a length of 817−−√ cm. what is the value of a (the length of bc¯¯¯¯¯¯¯¯)?