EXPLANATION :
We will discuss each line one by one.
5x + 1 = 21 is a Given
5x = 20
Note that the Subtraction property of equality states that if a value is subtracted from two equal quantities, then the differences are also equal :
[tex]\begin{gathered} a=b \\ \text{ Subtracting c from both quantities :} \\ a-c=b-c \end{gathered}[/tex]
Going back to our equation, subtracting 1 from both sides :
[tex]\begin{gathered} 5x+1=21 \\ (5x-1)-1=21-1 \\ 5x=20 \end{gathered}[/tex]
So the reason is Subtraction Property of Equality
x = 4
Note that the Division property of equality states that when dividing both sides by the same non-zero number, the two sides remain equal.
[tex]\begin{gathered} a=b \\ \text{ Divide both sides by c :} \\ \frac{a}{c}=\frac{b}{c} \end{gathered}[/tex]
Going back to our equation, dividing both sides by 5 :
[tex]\begin{gathered} 5x=20 \\ \frac{5x}{5}=\frac{20}{5} \\ \\ x=4 \end{gathered}[/tex]
So the reason is Division Property of Equality
