It’s here.
Here’s the math behind the problem.
What you’re doing is trying to solve for x. Think of large dogs as “x” and small dogs as “y.” 49 = x + y and y = x + 36 So, combine the two equations and you get:
49 = x + x + 36
49 = 2x + 36
13 = 2x
x = 6.5
y = 42.5