The M,E,U,E must appear in that order going left to right.
We must now insert the G, T, and R somewhere in these 5 blanks,
_____M_____E_____U_____E_____
So there are 5 places to put the G.
Regardless of which of the 5 blanks we put the G in, there
will be 6 places to put the T. To demonstrate that, suppose
we put the G between the U and the second E. And we see,
there are now 6 places to put the T. And it wouldn't matter
which of the blanks we had put the G in, it would still add
one more blank to put the T in.
_____M_____E_____U__G__E_____
By the same token, when we put the T in one of those 6 blanks,
it will add one more blank, and there will be 7 places to put
the R.
Answer: 5∙6∙7 = 210
Edwin