How can I solve this?

Write an equation of the function whose graph is described in words. The graph of y = cos(x) is vertically stretched by a factor of4 and shifted down by 9 units. One cycle of y = cos(x) on [0, 27:] is compressed to [0, n/3] and then the compressed cycle is shifted horizontally 15/4 units to left. y= 4cos(6x+ )9 x 4 M