Describe how you can use number relationships to tell whether the equation from question 3 (also below) is true or false without having to find the answer on both sides. 67 × 18 = (67 × 20) − (67 × 2)

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