Answer:
The question is not written correctly (and I couldn't find the actual question online), I assume that the actual question is:
"Angles A and B are complementary. If mL A = 2*x + 43 and mL B = 47°. Solve for x to find the measure of L A."
So I can answer this in a step by step way:
First, two angles are complementary if the sum of their measures is equal to 90°
Then we must have:
mL A + mL B = 90°
If we replace these by the measures, we have:
2*x + 43° + 47° = 90°
Now we can solve this for x.
2*x + 90° = 90°
2*x = 90° - 90° = 0°
Then we must have x = 0°.