Start from
[tex]\dfrac{|10-7|}{4} - \dfrac{|-15+8|}{6}[/tex]
Perform the additions inside the absolute values:
[tex]\dfrac{|3|}{4} - \dfrac{|-7|}{6}[/tex]
The absolute value does nothing to positive numbers, while it switches the sign of negative numbers, so |3|=3 and |-7|=7:
[tex]\dfrac{3}{4} - \dfrac{7}{6}[/tex]
Transform both fractions so that they have the same denominator:
[tex] \dfrac{9}{12} - \dfrac{14}{12} = \dfrac{-5}{12} [/tex]