I assume you are asking for the answer to question 6 so thats what I have here. If you want the answer to the other one just say so and I can help you with that too :))
Okay so working backwards, we have 20 balloons at the end, and the last thing we did was give away half plus 8, so lets now do that exact operation except backwards:
20 + 8 = 28
28 x 2 = 56
Now we know we had 56 balloons just after 13 less than half were given away, so lets do that backwards too:
56 - 13 = 43
43 x 2 = 86
Therefore there were 86 balloons to start with :))
