Answer:
He must invest R297 521 today.
Step-by-step explanation:
The compound interest formula is given by:
Where A(t) is the amount of money after t years, P is the principal(the initial sum of money), r is the interest rate(as a decimal value), n is the number of times that interest is compounded per year and t is the time in years for which the money is invested or borrowed.
Banabas must pay his ex-wife an amount of R350 000 in two years’ time.
This means that 
Interest rate of 8.15% per annum compounded monthly:
This means that 
.
Amount he must invest today:
This is P. So
He must invest R297 521 today.
First convert the mixed number to a fraction: 1 5/6 = 11/6.
The least common denominator of 10 and 15 is 30. It's easiest to use trial and error to find the LCD. In this case, just multiply both numbers by 2 and see if that works. Since 15 doesn't go into 20, I tried multiplying 15 by 2 instead, and got 30, which is divisible by 2. If that doesn't work, move on to multiplying them by 3, then 4 four, and so on. However, in this case, it did work, so, since you multiplied 15 by two to get 30, multiply 7 by two to get the fraction 14/30. Then, since you multiplied 10 by 3 to get 30, multiply 2 by 3 to get 6/30. Then, add the two together to get 20/30 and simplify the fraction to 2/3.
2/10 + 7/15 Given.
6/30 + 14/30 LCD.
20/30 Add.
2/3 Simplify.
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