The measure of the third side must be less than the sum of the other two. That property is valid for all triangles.
For this question, call x the measure of the third side. So you must have
x < 4 + 3
x < 7 ft
The only option that satisfies the condition above is
option A) 5 ft.
I hope this helps. =)
B is the answer i'm positive
6( x - 4) = 7
6 x - 24 = 7
6 x = 7 + 24
6 x = 31
x = 31/6
6 ( 31/6 - 4) = 7
186/6 - 24 = 7
186/6 = 144/6 = 7
42/6 = 7
7 = 7
Multiply the binomials:
(3x + 4)(5x - 2)

Final answer
Option B is the final answer