The first man made fibre is

Rayon

Explanation:

Rayon developed for the first time in the late 19th century as a replacement for silk. Silk was expensive in those days as was an organic product made out of cocoons. Rayon was the first man-made fibre came to be known as an artificial textile material formed from cellulose obtained from plants. Rayon was a less expensive option for silk clothing and accessories.

tracks, burrows, eggshells, nests, tooth marks, or gastroliths

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer