List the 3 steps discussed for translating larger phrases into algebraic expressions

Well. Say for example the larger phrase is "a number decreased by eight equals twelve."

1. Assigning a variable to the unknown quanity, commonly X. 

2. Find two verbal expressions for the same value. 
   ex. "a number decreased by eight" and "twelve."

3. Write out a mathematical expression for each verbal expression.
   ex. x - 8 = 12

After that we would solve out for the answer to 8, which would be equal to 20. Hopefully that makes some sense to you. If needed I can explain some more!