The first step is to find the height labeled as a.
The smaller triangle on the right side has 2 angles given as 45 degrees and the hypotenuse is 12 SQRT(2). This means both a and b are the same length and is 12 units.
Now we have a = 12 and the angle between c and d is 30 degrees.
sin(angle) = opposite leg / hypotenuse (d)
sin(30) = 12 / d
d = 12/ sin(30)
d = 24