This is what we have:
\(\frac{x}{5} =a\)
what we want is for x to "stand alone": for this, we need to get rid of this 5. we can do this by multiplying both sides of the equation by 5:
\(\frac{x*5}{5} =a*5\)
if we both divide and mupliply the first numebr by 5, it just means 1, so we can skip it:
\(x =5a\)
