Explanation:
The sum of angles in a triangle = 180°
Therefore,
(7x - 6)° + (5x - 10)° + 52° = 180°
Collect the like terms and add
7x + 5x - 6 - 10 + 52 = 180°
12x + 36 = 180°
12x = 180 - 36
12x = 144
x = 144 / 12
x = 12°
From the above diagram,
Angle A = 7x - 6
A° = 7(12) - 6
A° = 84 - 6
A = 78°