Question 423985


{{{(r-8s+7)+(3r+7s)+(s+9)}}}

={{{r-8s+7+3r+7s+s+9}}}

={{{4r-8s+7s+s+16}}}

={{{4r-8s+8s+16}}}

={{{4r-cross(8s)+cross(8s)+16}}}

={{{4r+16}}}