My goodness, this is rather confusing in the way it is worded. Nevertheless, I will attempt to do what I can. Just please keep in mind that this is my own interpretation of the problem, and therefore could be... incorrect.
I think, to start out, we could set up the problem like so
15 + t ≥ 26
because t is not a set number.
Then all that is needed is to subtract 15 from both sides, and the equation becomes
t ≥ 11
So the resulting answer is t ≥ 11.
I hope that my interpretation helps.
-Toremi