Question 549721
you want to subtract 2x - cy from ax - by.
first of all, you are subtracting (2x - cy) from (ax - by).
your equation should be:
(ax - by) - (2x - cy)
when you remove parentheses, this becomes:
ax - by - 2x + cy
you can regroup the terms to get:
ax - 2x + cy - by
now you can factor out the common terms to get:
(a - 2)x + (c - b)y
you needed to group those terms in parentheses before you started.
then you needed to subtract the first term from second term and not vice versa.
then you needed to keep track of the sign changes as you removed parentheses.