we are given
The angle is at right angled
It means that it's angle will be 90 degree
Since, these angles are part of right angle
so, their sum must be 90 degree
so, we get
[tex] 4a+5+3a-6=90 [/tex]
now, we can solve for a
[tex] 4a+3a-1=90 [/tex]
[tex] 7a=91 [/tex]
divide both sides by 7
and we get
[tex] a=13 [/tex].............Answer
