For typographical reasons, brackets around matrices are omitted here.

1.

To get the matrix of T, make the given columns into the columns
of a matrix:

2 5 0

3 1 4

2.

Once [A | 1] is in RREF and becomes [1 | B], B is the inverse
of A. So the answer is the right half of the second matrix, i.e.

-51 21 2

29 -12 -1

-2 1 0

3.

The product is

2(0) + 1(-1) 2(3) + 1(1)

1(0) + 3(-1) 1(3) + 3(1)

or

-1 7

-3 6

which is also the matrix of SU (the matrix of the composition is the product of the matrices).