Common difference of first series 15, 19, 23, 27…= 4

Common difference of 2nd series 14, 19, 24, 29 .. =5

So common difference of the series formed by common terms = 4*5 = 20

First common term = 19

So series = 19, 39 , 59, … last term < 415

nth term = 19+20(n-1) = 20n – 1 < 415

so 20n < 416

n < 416/20 = 20.8

so n = 20