Answer:
∠L = 43°
∠M = 121°
∠N = 16°
Step-by-step explanation:
<u>Start by setting all sides equal to 180</u>
3x - 5 + 7x + 9 + x = 180
<u>Add like terms</u>
11x + 4 = 180
<u>Solve for x</u>
11x + 4 = 180
       - 4     - 4
       11x = 176
      / 11     /11
         x = 16
<u>Now, plug in 16 for all instances of x on the triangle and solve.</u>
∠L = 43°
∠M = 121°
∠N = 16°
 
        
             
        
        
        
If x=girls, 
then we have 3x boys. 
We know that all children are boys+girls, so x+3x, which is 4x and 4x is 48, so one x is 12. 
So there are 12 girls and 36 boys.
        
                    
             
        
        
        
remember to use SOH CAH TOA. THE SOLUTION THAT I GOT CAME OUT AS 15/8