Use the Order of Operations.
1 Parentheses
2 Exponents
3 Multiplication
4 Division
5 Addition
6 Subtraction
Addition, subtraction, multiplication.
Addition: The addition of two integers produces another integer.
Subtraction: The subtraction of two integers produces another integer.
Multiplication: The product of two integers is an integer.
Division between two integers can produce a rational number that is not in the set of integers e.g. 1/3
This only includes the four basic arithmetic operations, you can include exponentiation and the modulo operation if you want to for the same reasons as above.
Answer:
n = 24
p(a) = 10/24
p(b) = 15/24
[ p(a) + p(b) - [p(a) ×p(b)] ] -1 = answer
[ 35/24 - 6/24 ] -1 = 39/24 - 24/24 = 5/24
