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

So convert from feet to meters

1 foot=12 in
1 meter=39 in

so x times foot=meter
x times 12=39
divide both sdies by 12
x=39/12
x=3 and 3/12 or 3 and 1/4 or 3.25

so 525=(3.25 times 525) feet=1705.25 feet

so 4.2 to 1705.25
turn into fraction and simplify
1705.25/4.2=406.25/1

the ratio is 406.25:1