I don't understand how to do this question! Doesn't it just mean to find the inverse of matrix T?

Find a formula for T^-1 if

T(x1,x2) = (8x1 - 4x2, 6x1 - 6x2)

Therefore:

T^-1(x1,x2) = (_x1 + _x2,_x1 + _x2) ?

What's the matrix of T...

Wouldn't it be like:

[8 -4]

[6 -6] ?!

Thank you so much...I'm confused.