If (x - 1) / x = 20, then x =

X-1/x=20

Multiply both sides by x.

x-1=20x

x-1-20x=20x-20x (Subtract 20x from both sides)

-19x-1=0

-19x-1+1=0+1 (Add 1 to both sides)

-19x=1

-19x/-19 = 1/-19 (Divide both sides by - 19)

x=-19