congruent means that bot S and T are the same degrees
so we can set S and T equal to each other and solve:
2x +5 = 5x-25
subtract 2x from each side:
5 = 3x-25
add 25 to each side:
30 = 3x
divide both sides by 3 to get x
x = 30 / 3
x = 10
now we know x so replace x with 10 and solve for S
S = 2(10) +5 = 20+5 = 25
angle S = 25 degrees