In other terms, once factored, you can set each parenthesis equal to zero. So like for (x-1), you set to zero, and solve. This gives factors. If the x is outside of parenthesis, like the -4x, then there is a root of zero.
In this case. Factor by grouping, then you will have several parenthesis multiplied by each other. Set each to zero
Think of the equation as the 10 times as parts so if Halle read ten times as more than Janet then we do the equation 264/11 because we have to include Janet's part too so Janet read 24, one part of the total while Halle read 240, 10 parts of the total