The opposite angles of a parallelogram are congruent, so you have to set the values of each angle equal to each other and solve for x.
(10x-19)° = (7x+23)°
-7x -7x
3x-19 = 23
+19 +19
3x = 43
÷3 ÷3
x = 43
Then, substitute the value of x back into the equations.
(10x-19)°
(10(14)-19)°
(140-19)°
121°
(7x+23)°
(7(14)+23)°
(98+23)°
121°
