1/7+2x/3=(15x-3)/21  make all terms have a common denominator of 21
3+14x=15x-3  subtract 3 from both sides
14x=15x-6  subtract 15x from both sides
-x=-6 divide both sides by -1
x=6
*Notice the use of parentheses in this format to make it clear what the numerators and denominators are...
        
                    
             
        
        
        
if the diameter is 15, its radius is half that, or 7.5
![\bf \textit{area of a circle}\\\\A=\pi r^2~~\begin{cases}r=radius\\[-0.5em]\hrulefill\\r=7.5\end{cases}\implies A=\pi 7.5^2\implies A=56.25\pi \\\\\\A\approx 176.71459\implies A = \stackrel{\textit{rounded up}}{177}](https://tex.z-dn.net/?f=%5Cbf%20%5Ctextit%7Barea%20of%20a%20circle%7D%5C%5C%5C%5CA%3D%5Cpi%20r%5E2~~%5Cbegin%7Bcases%7Dr%3Dradius%5C%5C%5B-0.5em%5D%5Chrulefill%5C%5Cr%3D7.5%5Cend%7Bcases%7D%5Cimplies%20A%3D%5Cpi%207.5%5E2%5Cimplies%20A%3D56.25%5Cpi%20%5C%5C%5C%5C%5C%5CA%5Capprox%20176.71459%5Cimplies%20A%20%3D%20%5Cstackrel%7B%5Ctextit%7Brounded%20up%7D%7D%7B177%7D)
 
        
                    
             
        
        
        
Do not trust people that share links these people hack and put viruses into your phone/cumputers
        
             
        
        
        
Its the second one: 5n-3=12