PLEASE HELP!! WILL GIVE BRAINLIEST IF RIGHT what is the value of x + y for the system of equations?

y = 2/3x - 9
y= 8 - 2x

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)

What is 10+10+20 about the origin the square root of a triangle.

The curved part of the figure is the semicircle what is the best approximation for the area of this figure