Reply to @LSpice 's comment: (Sorry, I don't have enough rep to comment, so posted as answer)
I tested your example in mathml tester in Firefox, colspan and align don't have effect.
In MDN I find that the attribute names should be columnspan and columnalign in MathML.
<math xmlns="http://www.w3.org/1998/Math/MathML"> <mtable><mtr><mtd>1 + 1</mtd><mtd>= 2</mtd></mtr> <mtr><mtd columnalign="left" columnspan="2">and</mtd></mtr> <mtr><mtd>1 + 2</mtd><mtd>= 3</mtd></mtr> </mtable> </math> have the effect $\begin{aligned}1 + 1&= 2\\ \text{and}\ \ \\1 + 2&= 3\end{aligned}$