Always put the smaller number first.
Our brains are accustomed to thinking in a progressive linear fashion ...
... ie. we find it easier to remember numbers from smallest to biggest.
So ...
Six Eights are Forty Eight
is easier than
Eight Sixes are Forty Eight
The only exceptions to this rule are when the last number of the sum is also the last number of the answer.
So it's easy to remember that ...
Six Fours are Twenty Four
Seven Fives are Thirty Five.
But apart from that, if you get the highest number first ... reverse them.
Nine Sevens is difficult.
Seven Nines are Sixty Three ... easy!
Nine Fours is difficult.
Four Nines are Thirty Six ... Easy!