algebra toughy....?

Question

Rory claims: " I have $20 in quarters, half dollars, and one-dollar bills. I have twice as many quarters as half dollars, and half as many one-dollar bills as half dollars." Give a convincing argument to explain why he must be wrong.

Answer 1

20= 4x*.25 + 2x*.5 +x*1
20 dollars = quarters+half dollars+dollars
20= 1x+1x+1x
20=3x
indivisible logically/ does not equal a whole number

began with logic that half dollars was 2x intead of x for sake of doubling