Explanation:
Scale Factor (SF)
The scale factor is the number you multiply the real by to get the model, it can also be used the other way, for instance if a map's SF was 1in=1ft (or times 12) every 2 inches on the map would be 24 inches (or 2 ft) in real life.
If the SF is lower than 1 (a decimal like .7 for instance) then the result will be smaller (for Real to Model)
for the first one, 80 times the SF will equal 25
80 * X = 25
^Here is it in equation form, X being the scale factor
isolate X (or find what x equals by getting it by itself)
divide each side by 80
X = 25/80
simplify or divide
X = 5/16 or x = 0.3125 (Both of these ca.