Question 71971
Solve {{{p = (-x)/2 + 75}}} for x = 2, 7, 9, and 11
For x=2 substitute this value of x into the formula and solve for p.
{{{p = (-2)/2 + 75}}} Simplify.
{{{p = -1+75}}}
{{{p = 74}}} 
For x=7 substitute this value of x into the formula and solve for p.
{{{p = (-7)/2 + 75}}} Simplify.
{{{p = -3.5+75}}}
{{{p = 71.5}}}

You should have the idea by now so try the others on your own.
If you still have trouble, please re-post.