Terms : 12x, 3, 13, 4x
Like Terms : 12x and 4x, 3 and 13
Coefficients: 12, 4
Constants : 3, 13
The least common multiples of 2 and 3 would be 2 and 1 also 2 and is at its lowest multiple
Looking at the units, 756 meters divided by 6 m/s will give you the seconds that you need.
So for A) 756/6 = 126
For B, you take the answer from A, and subtract 18 seconds, which would make it 108. Then you take the distance, 756 and divide by 108, that will be the speed.