) Dara invests $800 at 12.5% per annum compound interest compounded half- yearly .What in his amount of
interest at the end of the first year?

Where is your question?

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.

None of the options you showed are it.

Basic algebra equation. first set up your equation: divide out 9.and now you are left with 2x + 4 = 8.