Find $\sin \angle ACB$.
Find $\sin \angle ABC$.
You can use the Law of sines :
sin (70) / 25 = sin C / 26 then sin C = .97728 C = ARCSIN ( .97728 ) = 77.76 degrees
Now, you should know there are 180 degrees in the sum of the interior angles of a triangle :
Then angle B = 180 - 70 - 77.76 = 32.236 degrees the sin of which is .5334