You can put this solution on YOUR website! 4x translates in English to "4 times some unknown number" or "4 multiplied by some unknown number"
Example: Say gas is $4 a gallon. If you buy x gallons, then you'll spend 4x (4 times x) dollars. So if you buy 2 gallons, then you'll spend 4*2 = 8 dollars (excluding tax).