Question 925859
Sine rule states that: (Sin A / a) = (Sin B / b) = (Sin C / c)

1. (Sin 76 / 18) = (Sin B / 20) = (Sin C / c) 
Sin B = (Sin 76 • 20) / 18 = 1.078...
B = Sin^-1 (1.078) = error
So the answer for number 1 is no solution.

2. (Sin 58 / 11.4) = (Sin B / 12.8) = (Sin C / c)
By using cross multiplication we can find the answer to B:
Sin B = (Sin 58 • 12.8) / 11.4 = 0.952...
B = Sin^-1 (0.952) = 72 degrees

now that we have two angles we can find the third angle by using this formula:
C = 180 - (A + B) 
C = 180 - (58 + 72) = 50 degrees

Now we have:
(Sin 58 / 11.4) / (Sin 72 / 12.8) = (Sin 50 / c)
Now we can use cross multiplication to find c:
c = (Sin 50 • 11.4) / Sin 58 = 10.3


So these are the answers:
B = 72 degrees
C = 50 degrees
c = 10.3

And always remember to write the degree sign where it is needed.