Mary was having a birthday. She thought the supplies would cost $35, but they actually cost $40. What was Mary's percent error? (Don't forget to put the percent sign in your answer.)

-12.5% error

Step-by-step explanation:

Step 1. Subtract the actual value (40) from the estimated value (35)

35-40 = -5

Step 2. Divide the results (-5) with the actual value (40)

-5/40=-0.125

Step 3. Find the percent by multiplying the result (-0.125) by 100

-0.125 * 100 = -12.5

Therefore, the percent error was -12.5%