Explanation:
pythagorean theorem states
c²=a²+b² where c is the longest line a is the base while b is the height thus
example
1)c²=a²+b²
12²=a²+8²
144=a²+64.
144-64=a²
80=a² a=√80. =8.9
2)c²=a²+b²
15²=4²+b²
225=16+b²
225-16=b²
209=b² b=√209. =14.45
3)c²=a²+b²
c²=5²+9²
c²=25+81
c²=106. c=√106. =10.295
I hope you have understood I will do the other ones simply
4)26²=18²+a²
676-324=a²
√352=a. a=18.761
5)10²-6²=b²
100-36=b² b²=64. b=8
6)c²=12²+9²
=144+81.
c² =225. c=15