When does it makes sense to use similar triangles to measure the height and length of objects in real life?

In trapezoid efgh, m∠gfe=63∘. identify m∠ghe. !

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¯¯¯¯¯¯¯¯)?

Can you me find the slope! (30 points)