Question 558170
You don't want addition and/or subtraction. Stick to multiplication, division and powers.
First, division:
{{{16d^(1/4)=40}}} --> {{{d^(1/4)=40/16}}} --> {{{d^(1/4)=5/2}}}
Now, powers:
{{{d^(1/4)=5/2}}} --> {{{(d^(1/4))^4=(5/2)^4}}} --> {{{d=625/16}}}