Eighteen years ago ivan was three times as old as his son but he is only twice as old now. how old is ivan?

(not a trick question.)

72

Step-by-step explanation:

Let Ivan's current age be g and his son's current age by s.

Then g - 18 = 3(s - 18), and

         g = 2s

Substituting 2s for g in the first equation, we get:

2s - 18 = 3s - 54

Grouping like terms, we get:

36 = s.

Thus, Ivan's son's age now is 36 years; Ivan is twice that, or 72 years.

step-by-step explanation:

x^2 -12x + 36 + y^2 = 36

x^2 + y^2 = 12x

r^2 = 12rcos(theta)

r = 12 cos(theta)

1/800 is the right answer