4m can' t be the third side because the second side, 12m must be less than the sum of the first and third sides and can't be 19m because 19 must be less than the sum of the first and second sides.
As a rule, the measure of a side of a triangle must be less than the sum of the measures of the 2 other sides
I run 1 mile every 6 minutes. My friend runs 1 mile every 7 minutes. Lowest Common Multiple: LCM ( 6, 7 ) = 42 minutes. Me : 42 : 6 = 7 miles My friend : 42 : 7 = 6 miles.
