For (1) you are on the right track. Where did it fail? You should have equations:
You can then solve for t.
For (2) if you draw the free body diagram you have forces in the vertical direction: where is the angle of the string to the first support. In the horizontal direction you have . And from the length of the string being A you have . From this you have enough to get the final expression, but it takes some playing around. I suggest you get this last expression into terms of .