Question 976382
Part of your question looks mistyped, but if you want the inverse of D(p)


{{{-6(D^-1(p))+240=p}}}


{{{-6*D^(-1)(p)=p-240}}}


{{{D^-1(p)=(p-240)/(-6)}}}


{{{highlight(D^-1(p)=-p/6+40)}}}