Answer:
90 degrees
Step-by-step explanation:
B is the corner and angle opposite of the side AC.
so, AC is becoming side c, and the other two are a and b (it does not matter which is which).
we use the enhanced Pythagoras formula for general triangles
c² = a² + b² - 2ab×cos(C)
in our example the angle C is named B.
but other than that we simply calculate
10² = 6² + 8² - 2×6×8×cos(B)
100 = 36 + 64 - 96×cos(B)
100 = 100 - 96×cos(B)
0 = -96×cos(B)
cos(B) = 0
=>
B = 90 degrees
