Question 178560
Work from the inside out,
{{{2y+(7(3(2y-5)-(8y-7))+9)=2y+(7(highlight((6y-15))-(8y-7))+9)}}}
{{{2y+(7(3(2y-5)-(8y-7))+9)=2y+(7(6y-15-8y+7))+9)}}}
{{{2y+(7(3(2y-5)-(8y-7))+9)=2y+(7(-2y-8))+9)}}}
{{{2y+(7(3(2y-5)-(8y-7))+9)=2y+(-14y-56)+9)}}}
{{{2y+(7(3(2y-5)-(8y-7))+9)=-12y-56+9)}}}

{{{2y+(7(3(2y-5)-(8y-7))+9)=-12y-47)}}}