1/3a (bc-3de)=f for b
can anyone explain this to me?

At the newest animated movie, for every 9 children, there are 4 adults. there are a total of 39 children and adults at the movie.

The length of a rectangle plus its width is 25 cm. the area is 156 square cm. what are the length and width of the rectangle? separate the answers with a comma.

The length of a shadow of the building is 36m. the length of the pole, which is perpendicular to the ground, is 1.9m. the length of the pole's shadow is 1.52m. what is the height of the building?