Answer:
14
Explanation:
First, we'll mark our unknown addend as a variable.
How about x?
So, now our equation is 7+x=21
Now we have to figure out what x is.
You could have done this in a number of ways.
Option 1: The Sub-Add
21-7=x
Option 2: Basic Addition (First Grade Edition)
21+x=7
Option 3: The really hard thing that could be avoided by doing one and two and is also really long to say so just don't do it
x+7=21
so x will equal the addend
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
Now count up all of the numbers past seven.
There are fourteen.
So x equals 14.
Told ya it was hard.
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