Solution: First, calculate the sum of the expressions: $(3u - 4) + (7u + 2) + (4u - 1) = 14u - 3$. Divide by 3 to find the average: $\frac{14u - 3}{3}$. Since $u$ is a positive multiple of 3 and $u^2 < 100$, possible values for $u$ are 3, 6. Testing $u = 3$: $\frac{14(3) - 3}{3} = \frac{42 - 3}{3} = \frac{39}{3} = 13$. For $u = 6$, $u^2 = 36 < 100$, but $14(6) - 3 = 81$, $\frac{81}{3} = 27$. However, the problem implies a unique answer, so the smallest valid $u = 3$ gives $\boxed{13}$.

Sun, 10 May 2026 18:05:36 +0000

Content under review