This shows one possible method hack of aligning the 2nd row of a MathJax gathered environment with surrounding text.
The original question with a better solution can be found here.
Some primary text \(\begin{gathered}\frac{2}{3}+1\\[-2pt]\text{second row of 1}\end{gathered}\) some more text.
Some random text here saying nothing.
Second text \(\begin{gathered}\frac{x}{y}+z\\[-2pt]\text{second row of 2}\end{gathered}\) some secondary text.
Some concluding text saying nothing.
This does not allow for wider text that results in wrapping. It's just a proof of concept.