by your owned 100 pennies.
again,consider, a different situation.this time you ‘owe’ 100 pennies to one of your friends.in this situation,it is far away of thinking what to buy,instead you are to think how to pay him back 100 pennies.
quite different situations, more precisely, the situations are ‘opposite’ to each other.
so,here, we have a pair of opposites,both regarding 100 pennies.so,if in the first case,you have 100 pennies,then how much do you have in the second case? yes,the opposite of what you had in the first situation.so what is the opposite of the number 100?
so let the amount you had in the first case be positive(which is more likely to name ‘positive’),so, 