Angle of elevation of C from B is 19.3 degrees. x is the distance between B and C. So
tan(19.3) = (h-1575.2)/x.....(1)
Angle of elevation of C from A is 16.8 degrees.So
tan(16.8) = (h-1240.8)/(1742.6 + x)......(2)
Substitute the value of x from equation 1 in eq.(2) and solve for h.