Question is in picture.. someone please explain this to me

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

Stefano accidentally dropped his sunglasses off the edge of a canyon as he was looking down. the height, h(t), in meters (as it relates to sea level), of the sunglasses after t seconds, is shown in the table. during its descent, the pair of sunglasses passed by a climber in the canyon 6 seconds after stefano dropped them. to the nearest meter, what is difference in elevation between stefano and the climber? 166 meters 176 meters 230 meters 240 meters its b.176 i took the test 166 is wrong and 176 is correct

Bob is putting books on a shelf and takes a break after filling 18 1/2 inches on the book shelf. the book shelf is now 2/3 full. how long is the entire bookshelf?