Stmt I tell us its + or * so SUFF

Stmt II tell us its * or / so treu and false INSUFF

Hence A)

(6X2)X4 = 6X(2X4)
is true if X is + or *
ans is not true for - /

A
3x2 > 3

check for all * - / +
you will find it valid for + and *
for + and * 6 2 4 expr also is ok
so A is suff


B
3x1 = 3
check for all * - / +
you will find it valid for / and *
for * above expr true [as solved 624 exp is true for + and *]
but for / it is not
hence insuff

PS:
We call this property as associative property
so * and + are associative operators
This will not be asked in GMAT