Answer:
x = 10
Explanation:
The perimeter is the sum of the 3 sides of the triangle.
Sum the 3 sides and equate to 250, that is
9(2x - 3) + 7x + 11 + x + 6 = 250 ← distribute parenthesis and simplify left side
18x - 27 + 7x + 11 + x + 6 = 250
26x - 10 = 250 ( add 10 to both sides )
26x = 260 ( divide both sides by 26 )
x = 10