Answer:
Assume you will invest fixed amount x at the starting of each month
S(12): (1.00625x)*(1.00625^(12)-1)/(1.00625-1) = 2000
x=160
you will invest fixed amount 160 at the starting of each month and get 2000 at the end of the year ,which compounded 7.5% monthly.
how much will you have invested at the end of the first year ?
160*12=1920
First define the variables:
c = amount of children
a = amount of adults
Next create the equations to satisfy the conditions:
1) Total group is 12 people:

2) Total cost is $100 with adults costing $10 and children being $6:
