Juan has forty dollars in his jacket. Every day he spends half of the money that is in the jacket. On the first day (Monday), he spends $20 leaving him with twenty dollars. On what
day will he start with less than $3.00 in his jacket?
A) Friday
B) Thursday
C) Tuesday
D) Saturday

How do you use the elimination method for this question? explain, because i really want to understand!

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)

One hectometer is a) 1/1000 of a meter. b) 1/100 of a meter. c) 10 meters. d) 100 meters. e) 1000 meters.