Aladder is leaning against a building so that the distance from the ground to the top of the ladder is 8 feet less than the length of the ladder. find the length of the ladder if the distance from the bottom of the ladder to the building is 16 feet.

This is the concept of application of Pythagorean theorem and algebra;
Suppose the the length of the ladder is x ft, the distance from the ground to the top of the ladder will be (x-8) ft, the distance from the bottom of the ladder to the building is 16ft, thus to find the length of the ladder we proceed as follows;
c^2=a^2+b^2
x^2=(x-8)^2+16^2
x^2=x^2-16x+64+256
collecting the like terms we get:
x^2-x^2+16x=320
16x=320
solving for x we get:
x=320/16
x=20 ft
the answer is x=20 ft

The chemical reactions lab we did is typically called a "copper plating lab,  because the acid solution cleaned the pennies and made the copper look shinier;   the acid solution cleaned the paperclips and made them look like pennies;   &   the copper from the pennies was removed, and then added to the paperclips.