Actually Welcome to the Concept of the parallel,lines
Since both the angles are corresponding angles, hence they are equal,so we get as,
7x+40 = 3x+112
===> 7x - 3x = 112-40
===> 4x = 72
===> x = 72/4 => 18
hence x = 18°
now angle A = 7(18)+40
A = 166°
hence, A = 166°