Because anything multiplied by zero is zero, either the first pair of parenthesis is zero or the second pair is zero. Knowing this you take the number to put into x that makes it zero. For the first one it is 5. The second one is -0.75 because you put the 3 on the other side so you have 4x = -3. Then divide by 4 on both sides and you get x. Because there are two pairs of parenthesis, there are two answers.
In my opinion i dont think a bar model would be a good way of converting miles into feet because some might will get confused with a bar model and sometimes doesn't get you the accurate answer
