PEMDAS:
Parentheses, Exponents, Multiplication/Division (From left to right), Addition/Subtraction (From left to right)
There are no parentheses or exponents, so skip those steps. PEMDAS states we must deal with multiplication or division as it comes from left to right. Looking at the problem, multiplication comes first. So, do 6*3 = 18 first.
12 - 5 + 18 + 20 ÷ 4
Now do division
12 - 5 + 18 + 5
Now you must add/subtract from left to right. From left to right, subtraction comes first, so begin with subtraction then add.
7 + 18 + 5
25 + 5
= 30
30 is the answer