The required equation is,
→ 51° + U = 79°
Now we should,
find the required value of U.
→ 51° + U = 79°
→ U = 79° - 51°
→ [U = 28°]
Let's check whether the required value of U is correct or incorrect,
→ 51° + U = 79°
→ 51° + 28° = 79°
→ 79° = 79°
→ LHS = RHS
Hence, 28° is the required value of U.