The difference of twelve times a number and nine times a number

Since the problem states "a number" and again "a number", I assume it;'s the same number. Let the number be x.

12x - 9x = 3x

The difference of twelve times a number and nine times a number is three times the number.

i found two solutions,   n = 2 • ± √3 = ± 3.4641

step-by-step explanation:

- "runner b is moving at a slower rate."

- "the graphs shown are graphs of distance(km) against time(min).

the slopes of this graphs are are given by:

slope = (change in y)/(change in x)

= (change in distance)/(change in time)

this is the formula for finding the speed. so, the slope of these graphs represent the speed of the runner.

taking each division in the graph to represent 1 on both axis:

runner a ⇒ speed = (2-0)/(1-0)

= 2/1

= 2 km/min

runner b ⇒ speed = (3-0)/(3-0)

= 3/3

= 1 km/min

this shows that   runner b is moving at a slower rate."