Marc is looking at the plans for his new garage. the length of the garage is 8 metres. the scale on the drawing is 1: 50. what will the length of the garage be on the drawing?

The answer is 16 cm (or 0.16 m).

The scale is the ratio of the model to the real thing.
So, in the scale 1:50, the model is 1, while the real thing is 50.
Now, just make a proportion:
the model : the real thing = the model dimension : the real thing dimension
        1         :          50         =                   x                 :                    8m

From here:
x = 8m * 1 / 50 = 0.16 m = 0.16 * 100 cm = 16 cm.