Help me please solve this

Which is an equation for the nth terms of the sequence 12,15,18,21

Write an equation for the function that includes the points (1,4/5) and (2,2/3)

Thales was an ancient philosopher familiar with similar triangles. one story about him says that he found the height of a pyramid by measuring its shadow and his own shadow at the same time. if the person is 5-ft tall, what is the height of the pyramid in the drawing?