In the left hand side, you're multiplying 7.8 by 
In the right hand side, you're multiplying again 7.8 by a mysterious number.
So, the unknown number must be 
Every number remains unchanged when multiplied by 1, so the answer is 3.6
 
        
             
        
        
        
The correct answer is 77 degrees
        
                    
             
        
        
        
All the angles are different. And It's concave.
        
             
        
        
        
<span><span>
2−<span><span>2<span>(12)</span></span><span>(3)</span></span></span>−53</span><span> 
  =<span><span>2−<span><span>(2)</span><span>(36)</span></span></span>−53</span></span><span>
  =<span><span>2−72</span>−53</span></span><span>
  =<span><span>−70</span>−53</span></span><span>
   Answer :  <span>−<span>123</span></span></span>