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 = $\displaystyle 2Y + Y = 120g $

$\displaystyle 3Y = 120g $

$\displaystyle y = 40g $

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

taking moments about 'Q' $\displaystyle 40g \times 0.4m + 40g \times 1.6m = 588(0.8m-xm) + 20g \times 0.8m $

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