Question

Insira 5 meios aritméticos entre 12 e 54... 

Answer 1

a1=12
an=54
n=7
r=?

an=a1+(n-1).r
54=12+(7-1).r
54=12+6r
54-12=6r
r=42/6
r=7

(12,19,26,33,40,47,54..)