$$9x\ =\ 21\cdot27$$

$$27x=9\cdot21$$

$$21x=9\cdot27$$

$$x+27\ =\ 9+21$$

$$2\left(13\right)-5$$

$$2\left(13\right)-5+18$$

$$2\left(13\right)+1$$

$$2\left(13\right)+1+14$$

$$9+x=8+19$$  

$$9x=8\cdot19$$  

$$9\cdot8=19x$$  

$$9\left(9+x\right)=8\left(8+19\right)$$  

$$8\left(8+3x+4\right)=7\left(7+5x+2\right)$$  

$$8\left(3x+4\right)=7\left(5x+2\right)$$  

$$8\cdot7=\left(5x+2\right)\left(3x+4\right)$$  

$$8+3x+4=7+5x+2$$  

$$18x=24$$

$$18x^2=24$$

$$24^2=18x$$

$$24^2=18\left(18+x\right)$$

$$3x^2=9\left(9+16\right)$$

$$\left(3x\right)^2=9\left(16\right)$$

$$\left(3x\right)^2=9\left(9+16\right)$$

$$3x^2=9\left(16\right)^{ }$$