Need HELP with drawing the mass spectra graph!!!

the % abundance for each isotope will be 50% as half is one isotope and the other half is the other isotope

Is it always the same case for every isotope or just this one?

Just this one.

The height of the signal is directly proportional to the natural abundance of the isotope ...

I see, so this is the markscheme. How do I know the heights of 158, 160 and 162?!

This is statistics.

If you have two isotopes with equal probability and diatomic molecules then there are three possible masses for the molecules, 158, 160 and 162:

But there is twice as much chance (probability) of the molecule being 160

⁷⁹Br⁷⁹Br = 158
⁷⁹Br⁸¹Br = 160
⁸¹Br⁷⁹Br = 160
⁸¹Br⁸¹Br = 162

Hence the signal for 160 is twice as high ...

So if the question lets say was about Carbon for instance, do you work it out in the same way, so

C12 x C12
C13 x C13
C14 x C14

C12 x C13
C13 x C14
C12 x C14

C¹² x C¹³ x C¹⁴

Carbon cannot make diatomic molecules ..

It gets more complicated when the natural abundance of each isotope is not 50%.

In chlorine for example the ratio of heights for Cl₂ is 9:6:1, for 70, 72 and 74 respectively

How did you get the ratio?!