First let's see if (8, -2) can be written as a linear combination of (1, 1) and (1, -1): we want to find [tex]c_1,c_2[/tex] such that
[tex]c_1(1,1)+c_2(1,-1)=(8,-2)\implies\begin{cases}c_1+c_2=8\\c_1-c_2=-2\end{cases}[/tex]
Easily done; we find [tex]c_1=3[/tex] and [tex]c_2=5[/tex].
Since [tex]T[/tex] is linear, we have
[tex]T(8,-2)=T(3(1,1)+5(1,-1))=3T(1,1)+5T(1,-1)=3(4,3)+5(-1,1)[/tex]
[tex]T(8,-2)=(7,14)[/tex]