Suppose that 34% of the people who inquire about investments at a certain brokerage firm end up investing in stocks, 30% end up investing in bonds, and 35% end up investing in stocks or bonds (or both). What is the probability that a person who inquires about investments at this firm will invest in both stocks and bonds?

Answer 1

I get this but i can't remember what else I do

The "AND" are is shared. This is the key.

Abandoning the lengthy names:

A + S = 0.34 ==> S = 0.34 - A
A + B = 0.30 ==> B = 0.30 - A
S + B - A = 0.35

Answer 2

Suppose that % of the people who inquire about investments at a certain brokerage firm end up investing in stocks, % end up investing in bonds, and % end up investing in stocks or bonds (or both). What is the probability that a person who inquires about investments at this firm will invest in both stocks and bonds?