Given that AI = A, if A is a 3 x 3 matrix, what is the identity matrix?

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

Write the expression 7x^3-28xy^2 as the product of 3 factors

I'm a polygon i have no parallel lines i am formed 3 line segments i have one right angle two of my angles are angles what am i