Is there more context to the question?
Answer:
s = 13 - x
t = 
Step-by-step explanation:
To start out with:
s = 18
t = 18
Sue gives Tony x sweets
s = 18 - x
t = 18 + x
Sue then eats 5 of her sweets
s = 18 - x - 5 = 13 - x
t = 18 + x
Tony eats half of his sweets
s = 13 - x
t = 
(Possible constraint that
)
First divide 1/4=0.25 and then multiply 0.25 bu 100% so the result is 25%