Question

the sum of twice a number and 18 less than the number is the same difference between -30 and the number. What is the number?

Answer 1

X - the number

$2x+x-18=-30-x \\ 3x-18=-30-x \\ 3x+x=-30+18 \\ 4x=-12 \\ x=\frac{-12}{4} \\ x=-3$

The number is -3.