Answer: [tex]\bold{\dfrac{1}{2}(a-b)}[/tex]
Step-by-step explanation:
"half" means [tex]\dfrac{1}{2}[/tex]
"of" means multiply
"difference" means subtract
half of the difference between a and b
[tex]\dfrac{1}{2}[/tex] × ( a - b )
[tex]\large\boxed{\dfrac{1}{2}(a-b)}[/tex]