In the figure below, B is between A and C and C is between B and D. if BC=4, BD=12, and AD=15 and AC

AC = 7

Step-by-step explanation:

1. Draw out the line and label everything you know.

2. By observation, we know that AD is also equal to AC + CD.

3. To find CD, take the length of BD (12) and subtract it by the length of BC (4): 12 - 4 = 8. The length of CD is 8.

4. Finally, to find AC, subtract the length of CD (8) from AD (15): 15 - 8 = 7. The length of AC is 7.

the third picture

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."