6B(19): (3w+1)( t/3-wt)

我估你係想expand 佢

(3w+1)( t/3-wt)
= (3w+1)(1-3w) (t/3)
= (1 - 9w^2)(t/3)
= (t - 9tw^2)/3

I believe you want to factorize

(3w+1)(t/3-wt)

= (3w+1)(1-3w)t/3