The given expression is
![2\log _75+\log _7x=\log _7100](https://img.qammunity.org/2023/formulas/mathematics/college/jsfb7nzpkpcjdmncstbk6jqi64vd77wy0b.png)
First, we have to use the power property of logarithms, which states
![a\log x=\log x^a](https://img.qammunity.org/2023/formulas/mathematics/college/tnf8f3k7ybzfbqutc7cyypqqf6gi8rj196.png)
So, we have
![\log _75^2+\log _7x=\log _7100](https://img.qammunity.org/2023/formulas/mathematics/college/x8yw9c4ntwgfmmdhf161ws939r0wh4rmtu.png)
Now, we use the product property of logarithm, which states
![\log a+\log b=\log a\cdot b](https://img.qammunity.org/2023/formulas/mathematics/college/72145klzu9qnj1euii4htbvpul184ykinc.png)
Then, we have
![\log _75^2\cdot x=\log _7100](https://img.qammunity.org/2023/formulas/mathematics/college/x222ym99q34bc1szfxfzb8j7mepicln341.png)
We can eliminate logarithms
![5^2\cdot x=100](https://img.qammunity.org/2023/formulas/mathematics/college/ptqd3ajsr054xny5wpvs472jzq7gay4og1.png)
Now, we solve for x
![\begin{gathered} 25x=100 \\ x=(100)/(25)=4 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4d27686dewmceyjf4pm82xauwpb09m4vjg.png)
Therefore, the right answer is 4.