F(3) = 16, you simply plug in 3 for x to find the answer.
Complement means the other angle that will sum up to 90°
So:
x + 2x = 90°
3x = 90
x = 30°
So, it is 30° and 30 * 2°, or 60°
2 slices of watermelon. He divides it into 6 slices and 1/3 of 6 is 2m
Then the number must be between 18² = 324 and 19² = 361. But is that what you want to know?