The scale model of a skyscraper being built is 4.2 feet tall. when it is finished, the skyscraper will be 525 meters tall. what scale was used to make the model?

There are two scales that may be possible for this scale model; one where it's for every foot and one where it's for every meter.
The for every foot would be better to find out since the scale would be easier to use.
First, you have to divide each sided by 4.2, since you want to find how many meters for each foot.

For every 1 foot used in the model, the actual will be 125 meters.
1 ft = 125 m

20y5 times 2 is 1010 times -2 is -20, plus y