Hello! The situation (look the attachment).
I've made a system of three equations (using stack). I want to place lbrace
(which vertical size equals to two equations) bottom left beside the second and
the third equation. Math allows me only to place lbrace in the middle: the
vertical alignment is middle anyway.
There are some other ways to solve the problem: for example, to separate the
first equation from the rest ones. But I need all the three equations in one stack.
I think, it should be good to make possible a vertical alignment (maybe alignu,
alignd and alignm).