Can some one explain to me how to do these three problems so that i can do the rest of my home work. you

1.4²+b²=3.1²
1.96+b²=9.61
b²=7.65
b=√7.65
b=2.8(rounded to the nearest tenth)

5²+12²=C²
25+144=c²
169=c²
c=√169
c=13cm

6²+3²=c²
36+9=c²
c²=45
c=√45
c=6.7ft ( rounded to the nearest tenth)

A² + b² = c²
1.4² + b² = 3.1²
1.96 + b² = 9.67
-1.96         -1.96
           b² = 7.71
            b ≈ 2.78

a² + b² = c²
5² + 12² = c²
25 + 144 = c²
169 = c²
13 = c

a² + b² = c²
6² + 3² = c²
36 + 9 = c²
45 = c²
6.71 ≈ c

127 millimeters is the answer