Ascientist studied four rock rock fossils that show evolution of the modern day horse dating back to 35 million years, 15 million years, 8 million years, and 1 million years ago. which rock fossil is most similar to the modern day horse

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

the answer would be knowledge about cars!