The chest of drawers sold for half as much as the treadmill, for a price of $100/2= $<<100/2=50>>50.
The television sold for three times what he earned for the treadmill, for a price of $100*3= $<<100*3=300>>300.
For the three items, he raised $100+$50+$300 = $<<100+50+300=450>>450.
If $450 is 75% of the total sum of money that Toby made at the garage sale, then the total amount is $450 / (75/100) = $600.
#### 600