Help please, I don’t understand this question.

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¯¯¯¯¯¯¯¯)?

What is the value of the expression 9+n/3-6 when n = 12? 1. 5. 7. 12.

Somone me i want to know what 18 hours out of 24 hours in a fraction