How do you solve this 18(6-c)+13c=123

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)

If the segment op is dilated by a scale factor r=2, what is the length of segment op? a)10cm b)16cm c)6cm d)4cm

From a group of 10 men and 8 women, 5 people are to be selected for a committee so that at least 4 men are on the committee. howmany ways can it be done?