Explanation:
We want to isolate
b
in
a
+
b
+
c
=
180
.
Subtract
a
from both sides.
a
+
b
+
c
+
−
a
=
180
−
a
b
+
c
=
180
−
a
Now, subtract
c
from both sides.
b
+
c
−
c
=
180
−
a
−
c
b
=
180
−
a
−
c
a + b - c = 180
add c to both sides:-
a + b = 180 + c
subtract 180 from both sides:_
a + b - 180 = c ANswer