Asoma dos termos da p. a. (5+x,10+x,15++x) e igual a 1110.qual...

A1 = ( 5 + x)
a2 = ( 10 + x)
r = ( 10 + x) - ( 5 + x) = 10 + x - 5 - x = 5
an = a1 + (n-1)r
( 100 + x) = ( 5 + x) + (n-1)5
100 + X = ( 5 + X ) + 5n - 5
100 + x = x + 5n
100 + x - x = 5n
5n = 100
n = 20

S20 = ( a1 + a20 )* n/2
1110 = ( 5 + x + 100 + x ) * 10
( 2x + 105)* 10 = 1110
20x + 1050 = 1110
20x = 1110 - 1050
20x = 60
x = 60/20 = 3​