Answer: See explanation
Step-by-step explanation:
Your question isn't complete but let me help out.
To get an expression that is equivalent to 18 - 7, you will have to know the value of 18-7 first. This will be:
= 18 - 7
= 11
Since we know that 18-7 = 11, then from the options that you're given, you'll find the one that is also equal to 12 which will be the answer.
For example, let's say you're given the options of a. 20 - 6 and b. 3 + 19 - 11.
20 - 6 = 14. This means that it isn't an equivalent of 18-7.
3+19-11 = 11. So, this is an equivalent of 18-7.