Final answer:
The value of xx decreased by 79% is represented by the expression 0.21x, which means the original value is multiplied by 0.21.
Step-by-step explanation:
The value of xx is decreased by 79%. To calculate this, we start with the full value represented as 1 (or 100%) and subtract 0.79 (79%) from it, giving us 0.21 (21%). Thus, the expression representing the decrease in value of xx by 79% is 0.21x. If x represents the original value, multiplying it by 0.21 gives us the decreased value.
The value of x is decreased by 79%. To represent this situation, you would multiply x by 0.21, since it represents 21% of x. Therefore, the expression that represents this situation is 0.21x.