7th grade math again Imao sorry but ik its a lot but plss

17: -15x +0
18: -17x= -204
19: 21= -7n
20: m/4 = -13
22: -143= 11x
23: -16 + x = --15
26: n-8=-10
27: v/7 =8
28: a+11=20
30: 18+m=8

Astudent draws two parabolas both parabolas cross the x axis at (-4,0) and (6,0) the y intercept of the first parabolas 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