To simplify this expression, we first need to find a common denominator for each of the fractions:

19/24 can be written as 15/20
4/15 remains as 4/15

7/10 can be written as 21/30
6/15 can be written as 12/30

Now we can plug in the new fractions into the expression:

$15/20-4/15$ - $21/30-12/30$

Now, we can simplify by finding the common denominator for each set of fractions in the parentheses:

$(225/300-80/300)-(126/300-72/300)$

Now we subtract the fractions inside the parentheses:

$145/300$ - $54/300$

Now subtract the two fractions:

145/300 - 54/300 = 91/300

So, the final answer is 91/300.