I believe they just want you to add here, so for: a. 12,419,293+100,000 b. 12,419,293+1,000,000 c. 12,419,293- 10,000
the increase is addition and decrease is subtraction. If you're having trouble adding and subtracting them put them over each other and subtract or add them like: 12,419,293 + 1,000,000 -------------------
