If we know that y is directly proportional to x and that when x=1, y=3, then what is the value of x when y=4?

The fact that y is directly proportional to x gives us that y=kx, where k is some constant.Firstly, we need to find the value of this constant, using the pair of values we are given in the question. We substitute x=1 and y=3 into the equation y=kx. This gives 3=k*1, showing that k=3.Therefore the relationship between y and x can be written as y=3x. We then substitute y=4 into y=3x, giving 4=3x. Dividing through by 3 gives that x=4/3