The artist thought a decrease of 14% over the original tile 50 x 50, that's why she thought 49 x 49 was wrong.
But when she calculated she correctly calculated a decrease by 14% over the 57 x 57 tile that's how she had the same results.
1) Since the ceramic artist is aware that clay shrinks by 14% then the calculation should be:
2) So since the dimensions will shrink it, then this artist correctly calculated the new tile to 57 x 57 (since squares have the same length and width)
2.2) When the clay was in the oven, it shrank following this equation (minus 14%):
She thought that there was an error, probably because she calculated
a decrease of 14% of that original tile would yield a 43 x 43 tile, instead
of 57 x 57 Because: 50x ( 1-0.14)= 43.
3) Hence, the answer is:
The artist calculated a decrease of 14% over the original tile 50 x 50, that's
why she thought 49 x 49 was wrong.