Power Of Moat In Investing

What is investment ?

Raghu earns 25% on an investment but loses 10% on another investment. If the ratio of the two investment is 3:5. What is the gain or loss on two investments taken together ?

1500 in invested in two such part that if one invested at 6%, and the other at 5% the total interest in one year from both investments is 85. How much invested at 5% ?

From past experience it is known that an invester will invest in security A with a probability of 0.6, will invest in security B with a probability 0.3 and will invest in both A and B with a probability of 0.2. What is the probability that an investor will invest neither in A nor in B ?