For this question, we are looking for the relationship between y and b. One way to answer this question look at the pattern and notice that as b increases by 1, y increases by 6. Since y increases at a rate 6x faster than b, then we know y = 6b (answer choice c)
To solve this in a more mathematical and consistent way, we can use the formula y = Mx + B where x and y are the variables, m is the slope of the line, and B is the y-intercept of the line (note that for the purposes of question we will be substituting x with b and the B that represents the y-intercept is not the same as the b that represents blue paint).
The ratio between the blue and yellow paint can be found by solving for M. The formula for M, the slope, is as follows: M = (y2 - y1)/(b2 - b1) where two points on the line are (b1, y1) and (b2, y2). Given this information, we can take any two points from the chart an plug them into the formula. For example, if I choose the first two points of (1,6) and (2,12), I would solve for (12-6)/(2-1) = 6/1 = 6. Therefore, I know that y = 6b