Explanation:
t^2-11t=-18
first you collect like terms
t^2-11t+18=0
then you find the factors of 18t^2 in which the sum of the factors gives -11t. The factors are -9t and -2t
substitute -9t and -2t for -11t
t^2- 9t-2t+18=0
then you factorise
t(t-9)-2(t-9)=0
(t-2)(t-9)=0
t-2=0 or t-9=0
t=2 or t=9