Answer:
Given
¯¯¯¯¯¯¯¯¯
D
A
C
is a straight line, we can say its full measurement is 180°. If we know a segment of this angle,
∠
D
A
B
, is 105°, we can know that the other segment
∠
B
A
C
must equal 75, since
105
+
75
=
180
.
Once we've found the measure of
∠
B
A
C
to be 75°, and given the measure of
∠
A
C
B
to be 35, we can then find the measurement of
∠
A
B
C
.
Since we know that the sum of any triangle's angles is 180°, we can then use these known measurements as I said above.
75
+
35
+
m
∠
A
B
C
=
180
110
+
m
∠
A
B
C
=
180
m
∠
A
B
C
=
70
