Let's be x-number of $5 bills, then number of $1 bills will be 3x, and $10 bills x/2. Now let's count the money; $5 *x+ $1 * 3x+ $10 * x/2=260; 5x+3x+5x=260; 13x=260; x=20. Answer: there are 20 $5 bills, 60 $1 bills, 10 $10 bills. Checking: 20*5+60+10*10=260