Solve 4x - 3(20 - x) = -4 for x.

Step-by-step solution

1. 1

   Distribute the $-3$ across both terms in the bracket.

   $-3(20-x)=-60+3x$

   The second product is $(-3)(-x)=+3x$: the sign becomes positive. Writing $-60-3x$ is the single most common error, and it changes the answer completely.

2. 2

   Rewrite the equation without brackets.

   $4x-60+3x=-4$

3. 3

   Combine like terms. The two $x$ terms now add:

   $4x+3x=7x\quad\Rightarrow\quad 7x-60=-4$

4. 4

   Move the constant across.

   $7x=-4+60=56$

5. 5

   Divide and check.

   $x=\frac{56}{7}=8$

   Substituting back: $4(8)-3(20-8)=32-3(12)=32-36=-4$ ✓. So $x=8$.