If 9x x 3x+1 = 2187, what is the value of x?

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)a smart phone has dimensions of 4.9 inches (height), 2.3 inches (width) and 8.0 millimeters (depth). what is the volume of the smart phone in cubic centimeters? (1 in = 2.54 cm)

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

The diagonals of a quadrilaretral intersect at (-1,4). one of the sides of the quadrilateral is bounded by (2,7) and (-3,5) determine the coordinates of the other side in order for the quadrilaretral to be a square.