add v to t, add the result to u, then subtract what you have from s
Add v to t:
t + v
Add the result to u:
t + v + u
Then subtract what you have from s:
s - (t + v + u)
Add v to t:
t + v
Add the result to u:
t + v + u
Then subtract what you have from s:
s - (t + v + u)