Anumber increased by four is the same as 19 minus 2 times the number

From the information given, 4 added to the unknown number is equal to 2 times the unknown number when it is subtracted from 19.

Let the number be x

x + 4 = 19 - 2 (x)

We now expand and simplify the equation by placing unknown on one side and the known on the other side

x + 4 = 19 - 2x

x + 2x  = 19 - 4

       3x = 15

         x = 15 /3

          x = 5

- "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."