Answer:
9
Explanation:
In order for this problem to have more than one solution, one will have to make it such that the two sides are equal. Call the unknown quantity "x", and solve this equation like a literal equation;
5u + 3(4u - 6) = -3u - 27 + 20u + x
Simplify, (distribute and combine like terms);
5u + 12u - 18 = 17u - 27 + x
17u - 18 = 17u - 27 + x
Inverse operations;
17u - 18 = 17u - 27 + x
-17u - 17u
-18 = -27 + x
+27 + 27
9 = x