Answer:
23°
Step-by-step explanation:
Let the interior angles of ΔABC be referenced by A, B, and C. The definition of point D means that ΔDAB is an isosceles triangle, so we have the relations ...
A + B + 118 = 180 . . . . interior angles of ΔABC
A = B +16 . . . . . . . . . . base angles of ΔDAB
Using the expression for A in the second equation to substitute into the first equation, we get ...
(B+16) +B +118 = 180
2B + 134 = 180 . . . . . collect terms
2B = 46 . . . . . . . . . . . subtract 134
B = 23 . . . . . . . . . . . . divide by 2
m∠ABC = 23°