-- Call the number 'N'.
-- The sum of the number and six is (N + 6).
-- Twenty added to it is 20 + (N + 6)
-- That whole thing is twenty-seven
20 + (N + 6) = 27
Subtract 20 from each side: (N + 6) = 7
Subtract 6 from each side: N = 1
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Check:
Put your solution into the statement and see if the statement is true.
"Twenty added to the sum of (1 and six) is twenty-seven."
That's true. yay !