If you have 10 boxes and you shade 3 of these boxes, then the fraction of shaded boxes is 3/10. The fraction of unshaded boxes would just be the remainder of boxes, or 7/10.
-1/9+-5/9=
When you are adding a negative number, the operation turns into subtraction:
-1/9-5/9=

Really, it's just subtraction. The simplest form is -2/3, which is equal to -0.66667.
I hope this helps :)
This will be easier to write, and a lot easier to read, if we temporarily
use another symbol ... say, 'Q' ... to represent ' sin(2x) ' .
Here we go:
Original equation: Q² - 0.5 Q = 0
Factor the left side: Q (Q - 0.5) = 0
This equation is true if either factor is zero:
-- If Q=0, then sin(2x) = 0
2x = 0°, 180°, 360°
x = 0°, 90°, 180°
-- If (Q-0.5) = 0, then Q = 0.5
sin(2x) = 0.5
2x = 30°, 150°
x = 15°, 75°
The whole collection of solutions
between 0° and 360° :
x = 0°, 15°, 75°, 90°, 180° .
A + 2A = 180
3A = 180
A = 60
2A = 120A
3.5 divided by 4.
Each sister will receive 0.875 feet of ribbon.