There is only one property used to determine whether
[tex]4r+4t=4(r+t)[/tex].
The property is called the distributive property and in a nutshell it states, [tex]a(b+c)=ab+ac[/tex], which means [tex]a[/tex] is distributed through [tex]b+c[/tex] using multiplication. So [tex]4(r+t)[/tex] says, distribute [tex]4[/tex] to [tex]r[/tex] and [tex]t[/tex] which then translates into [tex]4r+4t[/tex].
