This is a right triangle. All side lengths of a right triangle can be found using Pythagorean Theorem.
1. 4^2+8^2=c^2, so this means that c=
80, so your first answer is 8.944.
2. 1600-625=a, so a is the square root of 975, which is 31.22.
3. c^2-a^2=b^2: 122,500-40000, so b^2 is 287.23.
4. 56.25+156.25=c^2, so c is 14.58
5. c^2-b^2=a^2, so a^2 is 67.8
Hope this helped.