Question

In a recent u.s.census, the population of Illinois was 12,419,293. What is this population after

Answer 1

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
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