Am going correct with this one.

Question

It is estimated that the Earth is losing 4000 species of plants and animals every year. If S represents the number of species living last year, how many species are on Earth this year?

S-4000=1
S=1+4000
S=4001 of species we have on this earth this year

Where did the 1 come from? The number on earth this year is S-4000.

I thought it was asking for me to solve. Or just the answer is s-4000

The answer is S-4000 if you posted the entire question. Unless there is more to the problem, the 1 has no place and S-4000 is the answer to the number of species on earth this year.