Find two numbers a a and b b whose sum a + b a+b is 0 and whose difference a − b a-b is 2. your answer is

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?

What is the missing step in this proof ?