Question

warm-up
who made the mistake?
zach
$28 - 8 \bullet 6 \div 3$
$20 \bullet 6 \div 3$
$120 \div 3$
$40$
kyle
$28 - 8 \bullet 6 \div 3$
$28 - 48 \div 3$
$28 - 16$
$12$
teacher graded question
what mistake did the student make?

Explanation:

Step1: Recall order of operations

Follow PEMDAS/BODMAS: Multiply/Divide first, left to right, then Subtract.

Step2: Analyze Zach's calculation

Zach did $28-8$ first (subtraction before multiplication/division):
$28-8=20$, then $20 \cdot 6=120$, then $\frac{120}{3}=40$. This violates order of operations.

Step3: Analyze Kyle's calculation

Kyle followed correct order: first $8 \cdot 6=48$, then $\frac{48}{3}=16$, then $28-16=12$.

Answer:

Zach made the mistake. He performed subtraction ($28-8$) before carrying out the multiplication and division operations, which violates the standard order of operations (PEMDAS/BODMAS, where multiplication and division are completed left to right before addition and subtraction).