If you would like to know how much does a 1-pound tub of butter cost, you can calculate this using the following steps:
3-pound tub of butter ... $3.85
1-pound tub of butter ... $n = ?
3 * n = 3.85 * 1
3 * n = 3.85
n = 3.85 / 3
n = $1.28
The correct result would be 3 * n = 3.85.