Answer:
x = 7
Step-by-step explanation:
The triangle inequality says that if we have a triangle of side lengths a, b, and c, then any of the following is true

In other words, the sum of any two side lengths is always greater than the third.
Now in our case, this means
![\begin{gathered} SA<7.5+3.5 \\ SAThis implies that [tex]7.5+3.5=x+9]()
which simplifies to give

subtracting 9 from both sides gives


which is our answer!