Difficult Trigonometry Problem

The problem is to find  
\[x\]
  in the problem below.

TRIGONOMETRY PROBLEM

\[OAB+ABO=90^o \rightarrow AOB=90^0\]
  and in fact all the angles at  
\[O\]
  are right angles. Let  
\[A)=x\]
.

TRIGONOMETRY PROBLEM

\[EO=x tan40, \: BO=xtan30, \: OC=(xtan30)tan10\]

TRIGONOMETRY PROBLEM

Then  
\[tan \alpha = \frac{(xtan30)tan10}{tan40}=0.1213 \rightarrow \alpha= tan^{-1}(0.1213)=6.92^o\]
.