3rs-8r+s-5rs+10r-s

This expression can be simplified by removing +s -s which cancel each other out and rearranging the order so that 'like terms' are grouped together, to produce

3rs -5rs -8r +10r

= -2rs + 2r

which can be simplified by factorizing using -2r which is common to both terms. Care to remember that this will therefore change the symbol inside the bracket:

**=-2r(s - 1)** or **-2rs + 2r**