Marcus thinks of a number between 5 and 10 He multiplies the number by 4 and adds 20.He takes this answer, multiplies it by 4 and adds 20 .He repeats this process a number of times and gets 868 What number did he begin with?

7

Step-by-step explanation:

7   ×   4   +   20   ×   4   +   20 = 212

212 x 4 + 20 = 868

Draw a perpendicular line segment from point M to the x-axis, and a perpendicular line segment from point L towards the thirst perpendicular.

The 2 perpendiculars meet at point A with coordinates (2, 1).  

Let P be the point located 3/5 the distance from L to M. This means that LP:LM=3:5. 

Draw a perpendicular segment from point P to AM. Let the intersection of these 2 line segments be B.

PB and LA are parallel. By Thales theorem, LP:LM=AB:AM = 3:5.

Since the length of segment AM is 8-1=7 units, then AB is 3 fifth of 7, 

that is AB = (3/5)*7=0.6*7=4.2 .

Thus, the y-coordinate of P, which is the same as the y-coordinate of B is 1+4.2=5.2 (units).

5.2