Using the information provided, in order to find Marco's starting balance we simply need to add all of his transaction costs together. Once we have this value we simply add it to his ending balance amount which will give us the total dollar value of his starting balance.
20 + 22 + 13 + 39 + 34 + 15 + 31 = 174
174 + 81 = $255
Finally, we can see that Marco's starting balance was a total of $255
If x is my daughter's age now, my age now is 4x. So now my daughter is 10 years old, and I'm 40 years old, and in 20 years she'll be 30 and I'll be 60, twice as hers.