A
- Harvard university professor
Working out the expression 7(3ˣ) is first to calculate the value of 3ˣ then multiply the answer to 7.
For example, let x = 2
Then 7(3ˣ) = 7(3²) = 7 × 9 = 63
With the same value of x = 2, calculating 21ˣ = 21² = 441, which isn't the same answer with the expression 7(3ˣ)
Answer:
answer in the pic
Step-by-step explanation:
If you have any questions about the way I solved it, don't hesitate to ask me in the comments below ;)

Method 1.
Use 

Method 2.

The solution to this equation is the number 8