Question 206912
A.  (2r-3s)(5r+7s)

Using FOIL (First-Outers-Inner-Lasts)

Take FIRSTS;  (2r)*(5r)

10r^2  (note it is r-squared, becuase, r*r is r^2; this is a common error, so watch out!)

Take OUTERS: (7s)*(2r)

14rs

Take INNERS:  (-3s)(5r)
-15rs

Then, ADD the outers and inners (because they are "like terms" in an equation, you MUST SIMPLIFY)

You get...  14rs + -15 rs = -(1)rs  or just -rs


Take LASTS:  -3s*7s

-21 s^2 (another "squared" to watch out for!)


Your final answer after making the puzzle...

{{{10r^2 -rs -21s^2}}}