If they have the same charge
x+x+x+x+x+x+x=-42
7x=-42
x=-6
so to check our answer
-6-6-6-6-6-6-6=-42
-12-12-12-6=-42
-24-18=-42
-42=-42
Answer:
∠ ABC ≈ 137.9°
Step-by-step explanation:
Using the Cosine rule in Δ ABC
cos B = 
with a = 89, b = 144, c = 65
cos B =
=
=
, thus
B =
( -
) ≈ 137.9° ( to the nearest tenth )
It is the first answer choice