(adding more to this but since the question only asked for one answer this should be enough!)
Step-by-step explanation:
a : 59
b : 59
c : 121
d : 121
f : 59
g : 90
h : 59
j : 31
k : 31 (everything in bold is uncited knowledge from me doing this years ago :,)
m : 90
so g must = 90 because not only is it in a right triangle, but also the corner of the rectangle. this goes for hk, m and jf, they all must add up to 90.
given a = 59 we can also find d from this, as it must add up to 180.
then adding g [90] + a [59] we get 149, which we then subtract from 180 to get j.
we get 31 from that and can now subtract 90 from that to find f, which is also 59, so f=59.
