Find the measure of x:

Hello! 13

Hope that helps!

x = 13

Step-by-step explanation:

You should note that any straight angle like those = 180° where they provided supplementary angles where the sum = 180°

(11x - 15) + (5x - 13) = 180°

Combine like terms:

16x - 28 = 180°

Add 28 on both sides:

16x = 208

Divide 16 on both sides:

x = 13

it would open into a square depending on the type of envelope i’m not sure about the second part