Lisa is now six years older than cheryl. in two years, lisa will be twice as old as cheryl. how old is lisa now?

Define x :

Let Cheryl be x years old.
Cheryl = x
Lisa = x + 6


In two years time:

Cheryl = x + 2
Lisa = x + 8


Lisa will be twice as old as Cheryl :

x + 8 = 2(x + 2)


Solve x :

x + 8 = 2(x + 2)
x + 8 = 2x + 4
x = 4


Find their age :

Cheryl = x = 4
Lisa = x + 6 = 4 + 6 = 10


Lisa is 10 years old now.

Num of plants = (original#ofplants)*(1.6)^t