Answer:
x = 6
Step-by-step explanation:
The sides are congruent; you can tell this by the lines marking the opposite sides (and, by viewing the shape, may recognize that this is a rectangle, which has congruent opposite sides).
Since these sides are congruent, we know that they are equal; therefore, we may set 40 = 5x + 10.
Now, solve with algebra!
40 = 5x + 10
30 = 5x
x = 6.
I hope this helped! :)
