First we use the distributive property to eliminate the parenthesis:
[tex]\begin{gathered} 12+3(7y-8)=12+3(7y)+3(-8) \\ =12+21y-24 \end{gathered}[/tex]Now we add similar terms and we get the following:
[tex]12+21y-24=21y-12[/tex]Notice that 21 and 12 are divisible by 3, therefore, we have::
[tex]21y-12=3(7y-4)[/tex]Finally, the simplifed expression of 12+3(7y-8) is 3(7y-4)
