Given:
Desmond deposits $ 50 monthly.
Yearly he deposits = $50×12 = $ 600
Rate of interest compounded monthly = 4.7%
To find the amount he will receive after 10 years and the rate of change the value of his account after 10 years.
Formula

where,
A be the final amount
P be the principal
r be the rate of interest
t be the time and
n be the number of times the interest is compounded.
Now,
Taking,
P = 600, r = 4.7, n = 12, t = 10 we get,

or, 
or, 
Now,
At starting he has $ 600
At the end of 10 years he will be having $ 959.1
So,
The amount of change in his account = $ (959.1-600) = $ 359.1
Therefore the rate of change = 
= 59.85%
Hence,
a) His account will contain $ 959.1 after 10 years.
b) The rate of change in his account is 59.85% after 10 years.
The answer is B. because it is 6:9 which simplifies down to 1:3
Whats the question? how many is she buying? or how many can she afford?
To find this, first find the factor or rate of which the numbers are moving. To do so do as follows.
subtract 1 from 3
3-1=2
So each number is having 2 added to it.
Now add two to 7 and the numbers afterwards till you get the 12th term
7+2=9
1+3+5+7+9
9+2=11
1+3+5+7+9+11
11+2=13
1+3+5+7+9+11+13
13+2=15
1+3+5+7+9+11+13+15
15+2=17
1+3+5+7+9+11+13+15+17
17+2=19
1+3+5+7+9+11+13+15+17+19
19+2=21
1+3+5+7+9+11+13+15+17+19+21
21+2=23
1+3+5+7+9+11+13+15+17+19+21+23
So 23 is the 12th term