There's not enough information.
They ate 181.5 pounds. If the baby panda ate x pounds, then the male panda ate 3x pounds. But we don't know how much did the female ate, or something about her. If we suppose the female panda ate y, then you could use this ecuation:
181.5 - x - 3x = y
181.5 - 4x = y
But there are many answers to that.