Since the total number of tomatoes is a third of a total, and you have the third of the total, all you have to do is multiply it by 3, so you get the equation 3x.
Say you have the equation 5(5x+7)=155 First you multiply 5 by everything in the parenthesis so you get 25x+35=155 then subtract 35 from both sides and get 25x=120 then 120 divided by 25 equals 4.8 so x=4.8
