The value of angle QRS is 41°.
The strategy is to use the fact that the exterior angle of a triangle is equal to the sum of the two interior opposite angles.
In the triangle formed by the points P, Q, and R, ∠QRS is an exterior angle. The two interior opposite angles are ∠ PQR and ∠RPQ.
Using the given information, we know that:
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We can now set up an equation to relate these angles:

Substituting the values we know:
(6x - 13)° = (x+18)° + (2x-4)°
6x -x -2x = 18 - 4 +13
6x - 3x = 18 + 9
3x = 27
Dividing both sides by 3 we get
x = 9
To find the value of ∠QRS put the value of x in the given value.
∠QRS = (6 x-13)°
∠QRS = 6 x 9 - 13
∠QRS = 54 -13
∠QRS = 41°