Question

Which equation could be used to solve this problem? The number of items on two grocery lists differs by 9. The total number of items for both lists is 33. How many items are on each list?

Answer 1

x + y = 33
x - y = 9 Add the 2 equations together
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2x = 42 Divide both sides by 2
x = 21

Use the original equation and plug 21 in for x, then solve.
x + y = 33
21 + y = 33
Subtract 21 from both sides
y = 12

One list had 21 items on it and the other list had 12 items on it.