Answer:the nth term of the sequence, Tn= -3n +12
Step-by-step explanation:
The nth term of an arithmetic progression is given as
Tn= a+ (n-1) d
where a= first term
and d = common difference
In this sequence, 9, 6 ,3 ,0, -3, -6 we can see that the number is decreasing by 3
The first term, a= 9
and common difference, d = -3
using our formulae
Tn= a+ (n-1) d
Tn= 9 + ( n-1) -3
Tn=9- 3n+ 3
Tn= -3n +12
In two years tom will become 10 years old
Because 5×2=10
For this case we must solve the following equation:

We apply distributive property on the right side of the equation:

We subtract 6y on both sides of the equation:

We subtract 6 from both sides of the equation:

Dividing by 6 on both sides of the equation:

So, the result is 
Answer:

All you have to is divide two consecutive terms to calculate the common ratio
1/4 divided by 5/12 = 1/4 * 12/5 = 12/20 = 3/5
I'd do 9x4=36 because the 9 is from your money and the 4 is from your books. Now since you want to find out how much 4 books cost you just multiply that by 9