Stats Help. Finding Sigma

Hey guys i am a bit confused with a problem for my statistics class. I am asked to find the Sigma (Standard Deviation). The question only gives me a few bits of information. And they are,

Desired Egg Weight is : 53 Grams
Average Weight of eggs layed by hens is : 48.8
And only 29% of the eggs exceed the desired amount.

How can i find the SD based off these numbers?

Thanks :)

I suppose you would set up the formula for a z-score.

Since 29% of the data is above, find the 71st percentile which has a z-score of 0.5534

Then set up the formula:

0.5534 = (53 - 48.8) / sigma

Solve for sigma and you get about 7.59