Which of the following is the correct formula for distance? (A.) d= (x2-x1)^2+(y2-y1)^2, where d is the distance between points (x1,y1) and (x2,y2).
(B.) d= sqrt (x2+x1)^2+(y2+y1)^2, where d is the distance between points (x1,y1) and (x2,y2).
(C.) d= sqrt (x2-x1)^2+(y2-y1)^2, where d is the distance between points (x1,y1) and (x2,y2).
(D.) d= sqrt (x2-x1)+(y2-y1), where d is the distance between points (x1,y1) and (x2,y2).

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