What's the question she got the answer wrong to?
The answer is B.
In order to add the two values together, you must find the least common multiple for the denominators. The denominators are 8 and 4, and the least common multiple of 8 and 4 is 8. Because you have to multiply 4 by 2 to get 8, you must also multiply 3 by 2 to get 6. This will give you 6/8.
-------------------------------------
Expression
-------------------------------------
5x - 3x
-------------------------------------
Substitute x = 2
-------------------------------------
5 (2) - 3(2)
= 10 - 6
= 4
-------------------------------------
Answer: 4
-------------------------------------
20/10 is same as 20:10 so the whole number is 2
