# How do you check that the solution to 2(5 - 2z) = 20 - 2(z - 1) is -5?

Jan 21, 2015

I'm afraid it's not. Expanding:
2(5−2z)=10-4z
and
20−2(z−1) = 20-2z+2
Now we can bring all the variables on the left, and all the numbers to the right:
$- 2 z = 20 - 10 + 2$
which yelds
$- 2 z = 12$
and thus $z = - 6$