Faye and andrew have written down the same negative number.
faye squares the number then multiplies by 2 and adds 4.
andrew multiples the number by 21 then subtracts the result from 40.
they both finish with the same answer. what was the number?

X - the number

Faye squares the number: x²
then multiplies by 2: 2x²
and adds 4: 2x²+4

Andrew multiplies the number by 21: 21x
then subtracts the result from 40: 40-21x

They both finish with the same answer, so the results are equal.


The number is negative so x=-12.

The number is -12.