To find the price to paint the entire wall, we just need to find the area of the wall and multiply by the price per square meter.
The area of a square is given by the product of the side length by itself. Since the measure of the side is 3 meters, the area is
[tex]A=3^2=9[/tex]9 m².
The unitary price per square meter is $1.50. Multiplying this value by the area, we have
[tex]9\times1.5=13.5[/tex]It will cost $13.50 to paint the wall.