Martin,

Solve your question in the same way I solve this one:

Three less than the sum of -4 and 6 times a number is -19.

First, I parse it all out:

"Three less than..."
-3 +

"...the sum of..."
-3 + ( ? + ?)

"...-4 and..."
-3 + (-4 + ?)

"...6 times a number..."
-3 + (-4 + 6n)

"...is -19."
-3 + (-4 + 6n) = -19.

So now I solve for n, the unknown number:
-3 + (-4 + 6n) + 3 = -19 + 3
-4 + 6n = -16
-4 + 6n + 4 = -16 + 4
6n = -12
6n / 6 = -12 / 6
n = -2.

My number is -2. Use the same idea to find your unknown number.

Cheers,
Stephen La Rocque.