Remark
Start with the product
Let the unknown number = x
The unknown number x is multiplied by 6
At this point you get 6x
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Now you add 15
6x + 15 = 9
Solve
6x + 15 = 9 Subtract 15 from both sides.
6x = 9 - 15 Collect the terms on the right.
6x = - 6 Divide by 6
x = - 6/ 6
x = - 1
