What is the length of the missing side?

6 ft

7 ft

9.21954446 (but round to what ever place is required)

Step-by-step explanation:

Use the Pythagorean theorem

a^2+b^2=c^2

6^2+7^2=c^2

36+49=c^2

85=c^2

c=9.21954446

round to what ever place you need