Alright. If we're multiply 3x by 3x, we can think of this as :
3 × x × 3 × x (since 3x is really just 3 × x)
We see that since it's all being multiplied together, it doesn't matter what order we do. 3 times 3 is 9, so we now have
9 × x × x
When multiplying the same type of variables, we add their exponents. if an exponent isn't shown, it's understood that there's an invisible 1 there. So we really have x^1+1 once we multiply x×x. So really, x × x is x^2. so, I now have:
9 × x^2 or 9x^2
I see that this isn't an available solution. Please recheck your answers, or what the original problem was. I can assure you that with the info provided, 9x^2 is undoubtedly the answer. Perhaps you meant 3x + 3x?
For the second problem, we just have to see how many times we need to add 5 to itself until we get 20. How many times we have to add is how many months he has to save.
5 + 5 + 5 + 5 = 20
So, 4 times, means he has to save for 4 months.
Hope this helps, and please let me know what happened with question 1!