$5\left( 3+3x \right)+7\left( 3-x \right)=4$
Distribute $5$ through the parentheses$15+15x+7\left( 3-x \right)=4$
Distribute $7$ through the parentheses$15+15x+21-7x=4$
Add the numbers$36+15x-7x=4$
Collect like terms$36+8x=4$
Move the constant to the right-hand side and change its sign$8x=4-36$
Calculate the difference$8x=-32$
Divide both sides of the equation by $8$$x=-4$