2/3b + 5 = 20 - b whats the answer here?

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¯¯¯¯¯¯¯¯)?

In the geometric progression –3, 12, −48… what term is 3,072?

Which image (a’ b’ c’ d’) of abcd cannot he produced using only reflections ?