Answer:
16
Explanation:
Use the method of PEMDAS (Parenthesis, Exponent, multiplication, division, addition and then subtraction.)
When using this order you would do 10-9 first
23 + 5 * (10-9) - 12
23+ 5 * 1 - 12
then 5 times 1
23 + 5 * 1 - 12
23 + 5 - 12
then 23 + 5 and subract 12 from the solution
23 + 5 - 12
28 - 12 =
16