Help please I’ll mark brainlist
I really needs help pls

Answer:
Step-by-step explanation:
base of 5 = 5 + 4 + 3 + 2 + 1 = 15
base of 10 = [tex]n^{2}[/tex]/2 + n/2 = 100/2 + 10/2 = 55
formula = [tex]n^{2}[/tex]/2 + n/2
where n is the number of base boxes