Robert starts out with $58.62 in his bank account. Then he makes a deposit of $142.76 because he got paid. The total in his bank account now is $201.38
Robert then decides to buy a new jacket that costs $63.76 which means he made a withdrawal from his account of $63.76 So you would now subtract the total in his bank account from the cost of the new jacket. This leaves him with $137.62 left in his bank account.
Next Robert bought two new movies, which each cost $6.99 and so because he bought two movies, you multiple $6.99 by two. This comes out to $13.98 which is the amount Robert paired to purchase the two new movies. Robert withdrew the $13.98 from his bank account, leaving him with $123.64 left in his bank account.
Finally, Robert is paid $12 for babysitting his younger sister. He adds this to his bank account, which means his bank account total is $135.64
This means that Robert now has $135.64 in his bank account.
You can combine the same numbers with the same variables using the operation sign for each. For example, using your equation, you would combine the 3n and 4n which is 7n. So your equation would be 7n - 2
