Declare variables:

- Let b be the number of business cards.

__Set up the cost function C(b) for Dunder Mifflin:__

C(b) = Cost to print each business card * b + Setup Charge

C(b) = 0.1b + 15

__Set up the cost function C(b) for Werham Hogg:__

C(b) = Cost to print each business card * b + Setup Charge

C(b) = 0.15b + 10

The phrase

*cost the same*means we set both C(b)'s equal to each other and solve for b:

0.1b + 15 = 0.15b + 10

Solve for

*b*in the equation 0.1b + 15 = 0.15b + 10

**Step 1: Group variables:**

We need to group our variables 0.1b and 0.15b. To do that, we subtract 0.15b from both sides

0.1b + 15 - 0.15b = 0.15b + 10 - 0.15b

**Step 2: Cancel 0.15b on the right side:**

-0.05b + 15 = 10

**Step 3: Group constants:**

We need to group our constants 15 and 10. To do that, we subtract 15 from both sides

-0.05b + 15 - 15 = 10 - 15

**Step 4: Cancel 15 on the left side:**

-0.05b = -5

**Step 5: Divide each side of the equation by -0.05**

-0.05b/-0.05 = -5/-0.05

b =

**100**