ANSWER
The substitution property of equality.
EXPLANATION
We know that:
[tex]12x = 60[/tex]
and that
[tex]x = 5[/tex]
Since x=5 or 5=x , we can substitute x for 5 wherever we see x in the given equation.
When we do that, we obtain;
[tex]12 \bullet \: 5 = 60[/tex]
This is what we refer to as the substitution property of equality.
