Explanation:
if there is nothing missing, we have
x + 25/-8 = -6
in order to compare or add or subtract fractions, we need to bring them all to the same denominator (bottom part).
remember, integer numbers are fractions too. like here
-6 = -6/1
25/-8 = -25/8
so, how can we bring -6/1 to .../8 ?
by multiplying 1 by 8.
but we cannot multiply only the denominator by 8. otherwise we would suddenly have
-6/8
and is -6/8 = -6/1 ? no, certainly not.
to keep the original value of the fraction we have to do the same multiplication also with the numerator (top part).
so, we actually do
-6/1 × 8/8 = -48/8
with this little trick we have now .../8 to operate with, and our transformed fraction has still the same value
-6/1 = -48/8 indeed.
so, we have
x + -25/8 = -48/8
x - 25/8 = -48/8
x = -48/8 + 25/8 = -23/8