Answer:
40
Explanation:
let the unknown be y (x is used as times(multiplication) )
(y-17)x-6=-138
add /-6 to both sides
y-17x-6/-6=-138/-6
y-17=23
make y independent/add 17 to both sides
y-17+17=23+17
y=40
or in an easier way
-138/-6 =23
23+17=40
simply reversing the question to get the answer