3.

Multiply both sides by abc to get rid of all division parts

−a^2b−a^2c−ab^2+abx−ac^2+acx−b^2c−bc^2+bcx=3abc

"Simplify"

x(ab+ac+bc) = a^2b+a^2c+ab^2+3abc+ac^2+b^2c+bc^2

Factor out x

x(ab+ac+bc) = a^2b+a^2c+ab^2+3abc+ac^2+b^2c+bc^2

Divide both sides by ab+ac+bc

x = (a^2b+a^2c+ab^2+3abc+ac^2+b^2c+bc2)/ab+ac+bc

Hope it helped.

By the way all exponents are alone, meaning they are NOT being multiplied by a variable or being added with other numbers. Sorry if it is confusing.