Question 1177080
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"Eighteen is..."
The "is" is the equals sign:
18 = ...<br>
"Eighteen is fifteen less than..."
"..fifteen less than..." indicates the 15 is going to be subtracted from something; we don't yet know what that something is:
18 = ??? - 15<br>
"Eighteen is fifteen less than the product of a number and three."
Now we know what the fifteen is being subtracted from -- the product of a number and 3:
18 = (x)(3) - 15<br>
That is how the mathematical statement looks if we translate the words as directly as possible.  In the usual mathematical form the statement would be
18 = 3x - 15<br>
Solve using basic algebraic steps.<br>
Add 15 to both sides to get the x term alone:
18+15 = 3x-15+15
33 = 3x<br>
Divide both sides by 3 to get x alone:
33/3 = 3x/3
11 = x<br>
ANSWER: the number is 11<br>