Answer:
1,900
Explanation:
Since there are 125 envelopes in each box, multiply the number of boxes by the number of envelopes:
18*125 = 2,250
Since she uses 350 of the envelopes, subtract it from the original number of envelopes:
2,250 - 350 = 1,900
So, Nicole has 1,900 envelopes left :)