Respuesta :

It is a rectangle so its opposite sides are congruent. Because they are congruent we can set them equal to each other and solve for x.

40 = 5x + 10
30 = 5x 
6 = x

So the value of x is 6.
The two sides are congruent so the value of x can be found with the equation 5x+10=40.

5x+10-10=40-10

5x=30

5x/5=30/5

x=6