First, represent the number that is unknown with a variable.
A variable is a letter that represents any number.
So let's use n to represent our number.
Now read through the problem.
If 3 times a number, that's 3n, is decreased by 5, -5, the result is 7, = 7.
So we have the equation 3n - 5 = 7.
To solve for n, we must first isolate the term
containing n which in this problem is 3n.
Since 5 is being subtracted from 3n, we add 5 to
both sides of the equation to isolate the 3n.
This leaves us with 3n = 12.
To finish things off, just divide both sides
of the equation by 3 to get n = 4.
So the number is 4.