Remember that
The intersecting chord theorem, states that the products of the lengths of the line segments on each chord are equal
so
In this problem]
we have that
(3x+1)*(30)=42*(x+11)
solve for x
90x+30=42x+462
90x-42x=462-30
48x=432
x=9
Find out the value of SU
SU=(3x+1)+30 ----> by addition segments postulate
substitute the value of x
SU=3(9)+1+30
SU=58 units
