Answer:
Step-by-step explanation:

Answer:
a3 = 45
Step-by-step explanation:
a1 = 20
an = a(n-1) *3/2 where n is the term number
a2 = a(2-1) *3/2
a1 *3/2
We know a1 = 20
a2 = 20*3/2 = 30
a3 = a(3-1) *3/2
= a2 *3/2
We know a2 = 30
= 30*3/2 = 45
Answer:
see below
Step-by-step explanation:
Let f = number of friends
all but one friend got 6 pieces and 1 friend got 2 for a total of 50 pieces
6(f-1) + 2 = 50
Subtract 2 from each side
6(f-1) +2-2 = 50-2
6(f-1) = 48
Divide by 6
6(f-1)/6 = 48/6
f-1 = 8
Add 1 to each side
f-1+1=8+1
f=9
Jack has 9 friends at the party
With Jack and his mom, there are 11 people
7:5 = 21:15
explanation : to get 21, multiply 7 by 3. since 7 is multiplied by 3, then you multiply 5 by 3 too. and you get 15.