Sally's teacher created a math problem but she colored the marbles with invisible ink please help by determining how many marbles in the bag were blue if the outcome of the probability of landing on green and choosing a blue marble is 5/21​

Astudent draws two parabolas on graph paper. both parabolas cross the x-axis at (–4, 0) and (6, 0). the y-intercept of the first parabola is (0, –12). the y-intercept of the second parabola is (0, –24). what is the positive difference between the a values for the two functions that describe the parabolas? write your answer as a decimal rounded to the nearest tenth