S1 a level cie help please

Can someone help me with the below question please , I really can’t solve it .

What are you having a problem with?

I just can solve it , I don’t know how ?

(can't?) What percentages take
Maths & Chemistry only
Maths & Biology only
then ...

Ok I tried everything ok ? I can’t get 0.3 which is the answer

Sorry, I thought you were asking about the 2nd part as you'd written the answer for the first part
Draw a venn diagram for the sets Biology and Chemistry
50% Chemistry
30% Biology
10% Both (overlap)
If you simply add Chemistry and Biology, is this right, if not how do you correct it?

I really really don’t get it , can you please elaborate a bit more , because I already know what u wrote I just can’t solve it , it says the answer is 0.3

I'm trying to get you to approach the problem. Have you drawn a venn diagram for the two sets, if not, try doing it. It makes the numbers clear.

I can’t draw it because I don’t understand , I’m really stuck .

The first example in
https://www.ck12.org/probability/venn-diagrams/lesson/Probability-Using-a-Venn-Diagram-and-Conditional-Probability-ALG-II/
is something like what you want. Have a think about how your problem maps onto it, what is similar, what is different.

Hey can you please help out with q 11 when you find the time

What do you understand about the problem? Its relatively straightforward.
* What outcomes are there?
* What is the probability of each outcome?
* What is the expected value?

I realized that, try starting to answer the 3 questions in the previous post.

I already solved all the questions I sent u before , I just have a hard time understanding 11 a ? Can u guide me through it ?

Try starting to answer the 3 points in post 13, I do know which question we're talking about.
If you don't understand what the possible outcomes are, simply guiding you through this question won't help in the long run.