#3/5r^2t(10r^3+5rt^3+15t^2)#
#=>3/5r^2t(5 (2r^3+1rt^3+3t^2))#
#=>3/cancel5r^2txxcancel5 (2r^3+1rt^3+3t^2)#
#=>3r^2t (2r^3+1rt^3+3t^2))#
#=>(3r^2txx2r^3)+ (3r^2t xx1rt^3)+(3r^2t xx3t^2)#---using distributive property
#=> 6r^(2+3) t + 3r^(2+1)t^3 +9r^2t^(1+2)#
#=> 6r^5t + 3r^3 t^3 + 9 r^2 t^3#
#=> 6r^5t + 3r^3 t^3 + 9 r^2 t^3#