Question 823429
We could set this up as a proportion.

{{{75/100}}}={{{x/87}}}
where x is the number we need to get right.
Cross products gives us
{{{100x=75*87}}}
{{{100x=6525}}}
Divide each side by 100
{{{ x= 65.25 }}}
If we cannot get partial credit, we
need to get 66 correct to be at 75% or above.