Let's start making our expression.
Just take the number 40 and change it around.

That's a good start.
49 is equal to 7×7, or 7². 9 is equal to 3×3, or 3².
So we can also write this as

You can really do whatever you want with it as long as it's still 40, just make sure you've got an exponent there. Here's another example.
Answer:
7200
Step-by-step explanation:
1,200 x 6 = 7200
Answer:
Step-by-step explanation: < 180
Answer: C, 7s + 3t and 3t + 7s.
Step-by-step explanation: Nothing is changing between the expressions except for their position. In addition, position does not matter though, so these two are the SAME EXPRESSION