The value of the number is 43.
The linear equations in one variable is an equation which is expressed in the form of ax+b = 0, where a and b are two integers, and x is a variable and has only one solution.
The subtraction property of equality states that when the same number is subtracted from both sides of an equality , then two sides of the equation still remain equal.
Let the number be x.
According to the given question.
The sum of the number and 21 is sixty-four.
⇒ x + 21 = 64
Now, we have a linear equation in one variable.
So, to find the value of the number we have to solve the linear equation in one variable.
Therefore,
x + 21 = 64
⇒ x + 21 - 21 = 64 -21 ( subtraction property of equality)
⇒ x = 43
Hence, the value of the number is 43.
Find out more information about linear equation in one variable and subtraction property of equality here:
https://brainly.com/question/17139602
#SPJ2