Write down the solution for this math problem: Solve -1992*u + 800*u + 909*u - 5377 = 0 for u.
answer: -19

Write down the solution for this math problem: Solve 7*s = 11*s + 16 for s.
answer: -4

Write down the solution for this math problem: Solve 630*a + 2210 = 153*a - 29749 for a.
answer: -67

Write down the solution for this math problem: Solve 18*s - 19*s = 0 for s.
answer:
0