Answer:
Step 4
Step-by-step explanation:
Given: Steps used by Shelly to evaluate the expression
To find: step that includes Shelly's mistake
Solution:
According to PEMDAS,
P denotes Parentheses
E denotes Exponents
M denotes Multiplication
D denotes Division
A denotes Addition
S denotes subtraction
Step 3 is and step 4 is
In step 4, first subtraction operation has been applied before the division operation.
There is a mistake in step 4 as according to PEMDAS, first -20 should be divided by 5 then 1 should be subtracted from the resultant number.