Pls help I really need it

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¯¯¯¯¯¯¯¯)?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.

Point m is located at (-4, -6). what is located 4 units from point m? ( its on a coordinate plane by the way. )