I'm trying to put the following three equations into a matrix:
$$x_1 + 2x_2 = 7\\ -2x_1 + 5x_2 = 4\\ -5x_1 + 6x_2 = -3$$
When I use the following
the resulting matrix is a mess, with no real column separation. Is there a way to specify columns in math mode? I know about presetting column separation widths, but I would rather it be done automatically, rather than as a presetting.