Hey there! :)
-15 = 3/4x
Let's start out by getting rid of our denominators -- we don't want any fractions here!
We can do this by multiplying EVERYTHING by 4. We do this because it's removing our denominator (which happens to be 4).
4 · -15 = 3/4x · 4
Simplify.
-60 = 12x
Divide both sides by 12.
-60 ÷ 12 = 12x ÷ 12
Simplify.
-5 = x
Therefore, x = -5
~Hope I helped!~