Answer:
12
Step-by-step explanation:
This is a joint variation problem:
z varies directly as x and y
Interpreting this;
z ∝ xy
Therefore;
z = kxy
z = 6, x = 2, y = 6
Now find k,
6 = 2 x 6 x k
6 = 12k
k = 
To find the value of z;
x = 3, y = 8
z = x 3 x 8 = 12
Given the recursive formula, each terms is five time the previous one.
This means that:
is 5 times 
, which means 
- in turn, is 5 times
, so we have 
. This means that 
- Finally,
So, substituting this back gives
In general, since you have 
, each time you compute a new term you multiply by a factor of 5, so if 
, you have
12+.60+ 12.60
12.60*20%
12.60*.20= 2.52
Tip should be around $2.52
Hope this helped :)
