A triangle is a triangle is two of the side lengths is greater than the third side.
A- (18+6= 24). (24>23). (13+6=19). (19>18). This is a triangle.
B- (13+22=35). (35>7). (22+7=29). (29>13). (13+7=20). (20<22) This is not a triangle.
C- (22+13=35). (35>8). (13+8=21). (21<8). This is not a triangle.
D- (6+18=24). (24>12). (12+6=18). (18=18) This is not a triangle.
The correct answer is A.
