To graph this line, move one of the points to positive three on the horizontal (side to side) line and negative six on the vertical (up and down) line. To get a slope of negative 1/2 you move down one point and right two points, and you continue until you reach the edge of the graph. Then you do the opposite on the way up (up one and left two).
This is a proportion. First you take the numerator times the denominator that is already solved. In this case you will take 5 times 7 and get 35. You then take 35 divided by 4 and get your answer.