Answer:
$0.25
0.25
Explanation:
5 / 20 = $0.25 per comic
Check.
0.25 * 30 = $7.50
Thus proves that $0.25 is the sale price per comic.
Constant of proportionality means a constant value the number goes up and since each comic costs $0.25, that is the constant or constant of proportionality.
Best of Luck!