Step-by-step explanation:
We can do a diagram of this problem first:
We have two similar triangles. One formed with the projector and the wall and another formed by the proyector and the screen.
The screen is half the distance from the projector to the wall away from the projector:
And since these triangles are similar (AA postulate), the ratio between the sides must be constant, therefore the image on the screen has to be half the width of the image on the wall:
Answer:
The image on the screen is 4.5 feet wide