b-a/3*2
The expression b-a/3*2 has the value 5. Because the multiplication and the dividing have the same priority, higher than the subtraction’s the highest priority operations execute from left to right (a divides to 3 then the result multiplies by 2). Then it executes the subtraction.

b-a/(3*2)
The expression b-a/(3*2) has the value 8. Firstly it executes the operations between parentheses, then the value of the variable a divides by 6, then the subtraction executes.