Hi there!
[tex]3 \sqrt{x} + 1 = 7[/tex]
Let's solve this equation step by step! In order to find the solution, we must get our x isolated.
First subtract 1.
[tex]3 \sqrt{x} = 6[/tex]
Now divide both sides by 3.
[tex] \sqrt{x} = 2[/tex]
And finally square both sides.
[tex]( \sqrt{x} ) {}^{2} = 2 {}^{2} \\ x = 4[/tex]
Check solution
[tex]3 \sqrt{4} + 1 = 3 \times 2 + 1 = 6 + 1 = 7[/tex]
This makes the original eqiation true.
Hence, our answer is x = 4.
~ Hope this helps you!