Answer: Sara would earn $478 for that week
Explanation:
1. Sara's weekly salaries is $400, and she gets 6.5% on sales at her work.
2. In order to find how much she would get from the commission of $1200 worth of merchandise they sold, we need to find the 6.5% of 1200
Step 1: Our output value is 1200.
Step 2: We represent the unknown value with x.
Step 3: From step 1 above, 1200=100%.
Step 4: Similarly, x=6.5%.
Step 5: This results in a pair of simple equations:
1200=100%(1).
x=6.5%(2).
Step 6: By dividing equation 1 by equation 2 and noting that both the RHS (right hand side) of both equations have the same unit (%); we have

Step 7: Again, the reciprocal of both sides gives

⇒

Therefore, 6.5% of $1200 is $78
3. you would then need to add 400 + 78 and you get a total of $478