I am stuck on question 4b, if anyone can have a look at my attachment and help ?

I keep getting a negative answer. Here's my working;

the reactions at point Q and R =

so the reaction at point q = 80g and reaction at point r = 40g, is this bit correct?

taking moments about 'Q'

is this moments equation correct? cause when I solve for 'xm' it gives me -0.26 ?