We can start off by knowing that perimeter is all the sides added together. That means that (2 1/2 x 2) + ((2 1/2 + x) x 2) = 19.
It would be easier to make this into decimals. 2 1/2 is the same as 2.5. Multiply this by 2 and you get 5.
Now you can do 19 - 5 = 14.
This means the other 2 sides have to equal 14 so you write an equation.
2(2.5 + x) = 14.
When you simplify, you get 5 + 2x = 14.
Subtract 5 from both sides and you get 2x = 9.
Solve for x and you get x = 4.5.
Your answer is x = 4.5