Use X and Y to represent the number of $10 and $50 notes respectively. Form 2 equations using the information given. Since there are 4 more $50 notes, the first equation should be Y($50)=X($10)+4. Second equation will be ($50)(Y)+($10)(X)=$380, this is to get the total amount of money. Sub equation 1 into equation 2. Solve for X, to get number of $10 notes.