Question

4 in 6 houses have a dog. There are 12 houses. How many have a dog? A: 6 B: 4 C: 8

Answer 1

C:8      Multiply by 2. Very easy

Answer 2

If 4 in six houses have a dog you can make that a fraction like 4/6.
The question is asking to have a 12 at the bottom of the fraction like x/12
to get to 12 from 6 you multiplied by 2. 
Multiply 4 by 2 and that is your answer.