What is the value of x?

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111°

Step-by-step explanation:

The polygon given is a heptagon having 7 sides.

Sum of interior angles of a 7-sided polygon = (n - 2)*180

= (7 - 2)*180

= 5*180 = 900°

Therefore:

126° + 158° + 120° + 125° + 121° + 139° + x° = 900°

Solve for x

789° + x° = 900°

Subtract 789 from each side

x = 900° - 789°

x = 111°

3x + 18 = 147°

step-by-step explanation:

3x + 18 = 147°, because the value of the central angle is equal to the value of the arc formed by it.

i hope i you.