Whats 851,708 to the nearest hundred-thousand

F(x)=x/2-2 and g(x)=2x^2+x-3 find (f+g)(x)

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?