Hints:
Step 1: Use Sine law the the angle B.
a/Sin A=b/SinB=c/SinC
24/Sin61^=12/SinB (accross multiply)
SinB=12Sin61^/24
SinB=0.437309853 then convert to degree =25.9 degree( depends on question rounded how many decimal) Read the question it must notes there.
--> Angle C=180-61-25.9=93.1 degree.
Step 2: Use Cosine law to calculate.
c^2=a^2+b^2−2ab⋅cosC
c^2=24^2+12^2-2(24)(12)cos93.1
c^2=720-576(-0.054078812)
c^2=720+31.11494
c^2=751.1494
c=27.4
(Square root take exponent off)
Explanation: