you need to find how much the output changes for each unit change in the input. (ie from an input change from 5 to 6 the output changes by three units and an input change of 3 (2 - 5 ) units the output changes by 9 units). This will give you the gradient of the equation. then you have to find out the y intercept by finding what the output is when the input is 0. Do this by multiplying the input by the gradient and then subtracting it from that inputs output. This will give you the answer A) 3x
