Question

Identify the variable in the expression $21+d$.

Short answer

The variable in the expression isd.

Step-by-step solution

Step 1. Apply the concept of Variable.

In any expression or equation, the variable is an unknown quantity. It may be any alphabet or any special symbol.

Step 2. Example for the variable.

In the expression $2x+3$, the unknown quantity is x. So, the variable in this expression is x. 2 and 3 are constants values.

Step 3. Identify the variable.

In the given expression $21+d$, 21 is a constant value while d is the unknown quantity.

So, the variable in the given expression is d.