Harry the Hungry Hippo is munching on the lily pads in his pond. When he arrived at the pond, there were $20$ lily pads, but he is eating $4$ lily pads an hour. Heinrick the Hungrier Hippo found a better pond with $29$ lily pads! He eats $7$ lily pads every hour.  

1. If Harry and Heinrick start eating at the same time, when will their ponds have the same number of lily pads remaining?

   Hint (a):

   Write an equation representing each hippo. Let $x=$ time (in hours) and $y=$ the number of lily pads. Note that the growth is negative.

   Hint 2(a):

   Harry's equation is $y=20-4x$.

   Hint 3(a):

   Set the two equations equal to each other and solve for $x$. They will have eaten the same number of lily pads when the equations for $y$ are equal.

   Answer (a):

   $x=3$ hours
   Don't forget to check your solution!

2. How many lily pads will be left in each pond at that time?

• Hint (b):

  Substitute $3$ back into one of the original equations and solve for $y$.