Explanation:
Given,
Angle A = 3x + 4
Angle B = 9x - 4
Angle C = 5x - 7
In ∆ABC apply angle sum property of triangle,
so,
Angle A + Angle B + Angle C = 180
after inserting the values we got,
3x + 4 + 9x - 4 + 5x - 7 = 180
17x - 7 = 180
17x = 180 + 7 = 187
x = 187/17
x = 11
hence , value of Angle A
= 3x + 4
= 3 (11) + 4
= 33 + 4 = 37°
hope this answer helps you dear...take care!