standard for is x × 10 ^I
where,
I = indice
10 > x < 0
you cannot write this is standard form with putting in what they stand for. However you can simplify it -
4(8m-7n) +6(3n-4m)
32m - 28n + 18n - 24m
8m - 10n
but hey I am from England do what we call standard form might be different