Concept: Sum of interior angle of triangle =180∘ Calculation: 1) 1:2:3 So, x+2x+3x=6x Then 6x=180∘,x=30∘ Angles 30∘,60∘ and 90∘ 2) 3:4:5 So, 3x+4x+5x=180∘ Then 12x=180∘,x=15 Angles 45∘,60∘ and 75∘ 3) 5:6:7 So, 5x+6x+7x=180∘ Then 18x=180∘,x=10∘ Angles 50∘,60∘ and 70∘ 4) 6:7:8 So, 6x+7x+8x=180∘ Then 21x=180∘,x=8.57∘ Angles 51.42∘,59.99∘ and 68.57∘ ∴ Option 4 is not integer angle in triangle.