You use it during your life spand
2n+5...a couple is two people so you need to multiply the number of couples, n, by 2 to get the total number of dancers. Then add the total number of organizers.
Answer:
Step-by-step explanation:
take 50*4.5 and you'll get your answer
the height:

(with g being the gravitational acceleration)
1) an = a1 + d*(n-1) => a20 = -4 + (-9)*19 = -4 - 171 = - 175
1) ---> C)
2) a81 = 20 + 4*80 = 340;
2) ---> A)
3) a12 = ?
3) ---> B) or D).