Ok so if I understand this correctly then you have to find out what each one of them are then add them to get the total number of both of them. So this is the equation I did. The one circled on blue is the formula I made for the equation and then the green one is the answer. which is 5 4/9
I hope this helps.
Answer:

Step-by-step explanation:

Hope this helps!
120 x 15 = 1800 :) thats the answer
Answer:
At the beginning of 6th month , Jeff will have in his account $ 520 .
Step-by-step explanation:
At the beginning of 6th month , Jeff will have in his account,
$ 
= $ 
= $ 
= $ 
= $ 520
since, the $ 100 deposited at the end of 1st month earns interest for 4 months till the end of the 5th month, the $ 100 deposited at the end of the 2nd month earns interest for 3 months and so on till the last $100 deposited earns interest for '0' month.