Question

Four times a certain number is equal to number subtracted by 40 find the number.

Answer 1

4 n = n - 40 ?

3 n = -40
n = -40/3
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-160/3 = -40/3 - 40 ?
-160/3 = -40/3 - 120/3 ?
yes
but I bet you meant subtracted FROM 40
4 n = 40 - n
5 n = 40
n = 8