Both numbers are divisible by 2.
but he wants the greatest number of columns we try 4 and it works we try 8 and it works we try 16 and it does not ! so the maximum number of columns that satisfies both numbers is 8
so both bands can be divided by 8 columns .
the high school band will have 8 columns having 12 marchers each while the middle school one will have 8 columns having 7 marchers each
12x8=96 ,7x8=56