Question

Jenny is working on simplifying the algebraic expression 3x+21
when x=5
. Her steps are as follows:

Step 1: 35+21

Step 2: 15+21

Step 3: 36

In which step did Jenny make a mistake? What should she have done differently?

(1 point)
Responses

Step 2, Jenny should've calculated the value of 35
to be 243.
Step 2, Jenny should've calculated the value of 3 to the 5th power to be 243.

Step 2, Jenny should've added 3 and 5 to get 8.
Step 2, Jenny should've added 3 and 5 to get 8.

Step 1, Jenny should've multiplied 3⋅5
instead of writing 5 as the exponent.
Step 1, Jenny should've multiplied 3 times 5 instead of writing 5 as the exponent.

Step 3, 15+21
should be 15⋅21
.

Answer 1

Jenny made a mistake in Step 1. She incorrectly evaluated \( 3 \cdot 5 \), which should give \( 15 \) instead of \( 35 \).

Here's what she should have done:

Step 1: Calculate \( 3 \cdot 5 \) which equals \( 15 \).

Thus, the correct expression after substituting \( x = 5 \) into \( 3x + 21 \) should be:

Step 1: \( 3 \cdot 5 + 21 = 15 + 21 \)

After that, she could correctly proceed to Step 2:

Step 2: \( 15 + 21 = 36 \)

Therefore, the mistake occurred in Step 1 where she should've multiplied \( 3 \cdot 5 \) instead of incorrectly calculating \( 35 \).