Which set of number cannot represent the lengths of the sides of a triangle?

a) 7, 9, 13
b) 8, 6, 7
c) 8, 19, 11
d) 9, 11, 16

provide explanation.

Without any equipment, you can see stars that are 2{,}800{,}0002,800,0002, comma, 800, comma, 000 light-years away. by looking through a small telescope, you can see stars that are 3{,}112{,}000{,}0003,112,000,0003, comma, 112, comma, 000, comma, 000 light-years away. approximately how many times as far can you see using a small telescope as without any equipment?