Solve for: 4.2(15+5x)=-20x-21-x

Expression: $4.2\left( 15+5x \right)=-20x-21-x$

Distribute $4.2$ through the parentheses

$63+21x=-20x-21-x$

Collect like terms

$63+21x=-21x-21$

Move the variable to the left-hand side and change its sign

$63+21x+21x=-21$

Move the constant to the right-hand side and change its sign

$21x+21x=-21-63$

Collect like terms

$42x=-21-63$

Calculate the difference

$42x=-84$

Divide both sides of the equation by $42$

$x=-2$