How do I get X on ax=a-3x?

Question

I would like the procedure, not only the result.

Answer 1

ax = a-3x if and only if
ax + 3x = a if and only if
(a+3)x=a if and only if
x = a/(a+3)

so assuming you know what a is, and a doesn't equal -3, the solution is x = a/(a+3)

Answer 2

ax = a - 3x
Add 3x to both sides to get all the x on the same side
Factor x from the common terms on the left side
Divide both sides by the result
Don't look any further down if you don't want the answer
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ax + 3x = a
(a+3)x = a
x = a/(a+3)

Answer 3

ax=a-3x
ax+3x=a
x(a+3)=a
x=a/(a+3)