I don’t really understand this can some help me with the right answer

Which three lengths could be the lengths of the sides of a triangle? 21 cm, 7 cm, 7 cm 9 cm, 15 cm, 22 cm 13 cm, 5 cm, 18 cm 8 cm, 23 cm, 11 cm

An air conditioning system can circulate 350 cubic feet of air per minute. how many cubic yards of air can it circulate per minute?

If f(x) = 4x – 3 and g(x) = 8x + 2, find each function value a. f[g(3)] b. g[f(5)] c. g{f[g(-4)]}