The value of x is 13°.
Solution:
In triangle, sum of all the interior angles = 180°
m∠A + m∠B + m∠C = 180°
(3x)° + (4x – 1)° + 90° = 180°
3x° + 4x° – 1° + 90° = 180°
7x° + 89° = 180°
Subtract 89° from both sides of the equation, we get
7x° = 91°
Divide by 7 from both sides of the equation, we get
x° = 13°
The value of x is 13°.