Read through the entire word problem. For example, "Joe has 1 inch of hair cut off his beard each time he goes to the barber. If b equals the length of his beard before he cuts it and c equals the length of his beard after he cuts it, write an equation to find the length of Joe's beard after he visits the barber. What length will his beard be if he started out at 4 inches?"
Write down the variables and the constants. Here, the variables are b (beard before being cut) and c (beard after being cut). The constant in this equation is 1 inch.
Form your equation by placing the variables and constants on the correct side of the equal sign. Here, you are solving for c, so c is on the left side of the equation. Additionally, the facial hair is being removed, which means the 1 becomes negative. So the equation should look like: c=b-1.
Plug in the stated number for the variable and solve your equation. Here the number to plug in is 4, so your equation becomes c=4-1, which means c=3 inches.