How to subtract mixed fractions with different denominators

$25 becasue a 10 increase would make it from 80 to 50

ok it is easy it is 3

let f: r - > r and g: r - > r be two functions defined by f(x) = x + 1 and g(x) = x - 1.

let us prove whether these functions are inverses of each other by using composition.

f·g (x) = f(g(x)) = f(x - 1)

                      = (x - 1) + 1

                      = x

also, g·f (x) = g(f(x))

                  = g(x + 1)

                  = (x + 1) - 1

                  = x

hence, f and g are inverses of each other.

clearly, f·g : r - > r.

therefore, the domain of f·g is r = (-∝, ∝).